Samāpatti, complete absorption of the mind when it is free from its vṛttis, occurs when the mind becomes just like a transparent jewel, taking the form of whatever object is placed before it, whether the object be the knower, the instrument of knowledge, or the object of knowledge.

Bryant Commentary:

Patañjali has considered various objects that can be used to support the mind in meditation. Now he returns to the analysis (begun in I.17) dealing with stages within the meditative state itself, irrespective of its object. When the mind is freed from all distractions in the form of the vṛttis, it becomes like a pure crystal, maṇi, says Vyāsa. Just as a crystal exactly reflects the color of whatever object is placed adjacent to it, so the peaceful and fixed mind is colored, añjanatā, by any object presented to it, and, in advanced meditation, actually inherently assumes the form of that object. The comparison expressed in this sūtra by Patañjali is encountered numerous times throughout the commentaries and has attained wide usage in Hindu philosophical circles: Just as a pure crystal shines with a red color when placed next to a red hibiscus flower, so the calm, pure, and luminous sāttvic mind, when freed from the effects of rajas and tamas, shines with the form of any object presented to it. This occurs when the mind is focused one-pointedly on the object in question. Patañjali states here that the mind can reflect and assume the form of any object: an external object made of gross or subtle elements, grāhya; the very instruments of knowledge themselves such as the sense organs, grahaṇa; or the intelligence, grahītṛ, the knower, even in its purest and most subtle function of indirectly being aware of puruṣa itself. This sūtra, as we noted, has influenced the commentators interpretation of I.17.

The gross and subtle elements evolve out of citta (intelligence and ego) in Sāṅkhya, and thus the mind, being more subtle than its evolutes and, indeed, their very essence, can pervade them. This includes not only the, objects of knowledge, that is, sense objects, but also, as Patañjali indicates here, the grahaṇa, instruments of knowledge, that is, the sense organs themselves, and the grahītṛ, faculty of buddhi, the knower. The mind can not only internally mold its own guṇas into the prākṛtic form of an object or sense organ, but can actually externally penetrate into the object’s very essence. In a sense it becomes the object by merging with it and thereby gains ultimate insight into its deepest nature. This is the samāpatti introduced in this sūtra. Additionally, when completely pure and steady, the mind can ultimately reflect puruṣa to itself, the penultimate stage of yoga practice.
Obviously, the mind cannot know puruṣa in its own true nature, as Śaṅkara points out, since it is inanimate and puruṣa is more subtle than the mind. Things can grasp or perceive only things grosser than themselves: The senses can grasp only the sense objects, but not vice versa; the mind can perceive the senses, but not vice versa; and the puruṣa can perceive the mind, but not vice versa. This is a favorite trope of the Upaniṣads: “That which one cannot grasp with one’s mind [ātman/Brahman], by which, they say, the mind is grasped” (Kena I.5). “By what means can one know the knower?” (Bṛhadāraṇyaka II.4.13). “You can’t see the seer who does the seeing; you can’t hear the hearer who does the hearing; you can’t think the thinker who does the thinking; you can’t perceive the perceiver who does the perceiving” (Bṛhadāraṇyaka III.4.2). “Sight does not go there, nor does thinking or speech. We don’t know it, we can’t perceive it, so how would one express it?” (Kena I.3). “Not by speech, not by the mind, not by sight can he be grasped. How else can that be experienced, other than by saying ‘He is’?” (Kaṭha VI.12). “The self cannot be grasped by multiple teachings or by the intellect” (Muṇḍaka III.2.3). Only puruṣa can know itself. But mind can, however, redirect awareness back to its own original source and thus indirectly reflect puruṣa, just as a mirror can reflect a face. In other words, puruṣa can become aware of itself by means of the reflective nature of the pure sāttvic mind.

Although samāpatti, introduced in this sūtra for the first time, and samādhi can be correlated in a general way, and the states of mind they represent overlap, they are not technically synonymous: Vijñānabhikṣu points out that the various types of samāpatti occur as results of samprajñāta–samādhi. Samādhi in general might best be understood in terms of the goal of yoga: the state when all vṛttis of the mind have been stilled. Samāpatti is, more specifically, the complete identification of the mind with the object of meditation. Put simply, the former is the more general or overall state of the stilled mind, the latter the more specific content or object upon which the mind has settled itself in order to become still. Complete mental identification with and absorption in an object, by definition, can obviously occur only when all other vṛttis have been stilled and the mind is without distraction; hence samāpatti occurs only in the context of samādhi as indicated in this sūtra.

Tapas (Austerity Or Sturdy Self-Discipline—Mental, Moral And Physical), Svadhyaya (Repetition Of Sacred Mattras Or Study Of Sacred Literature) And Isvara-Pranidhana (Complete Surrender To God) Are Kriya-Yoga (Yoga In The Form Of Action).

Yogic action has three components—discipline, self-study, and orientation toward the ideal of pure awareness.

The practical means for attaining higher consciousness consist of three components: self-discipline and purification, self-study, and devotion to the Lord.

Austerity, self-study and resignation to Isvara constitute preliminary Yoga.

Taimini Commentary:

The last three of the five elements of Niyama enumerated in II-32 have been placed in the above Sutra under the title of Kriya-Yoga. This is rather an unusual procedure and we should try to grasp the significance of this repetition in a book which attempts to condense knowledge to the utmost limit. Obviously, the reason why Tapas, Svadhyaya and Isvara-Pranidhana are mentioned in two different contexts lies in the fact that they serve two different purposes. And since the development of the subject of self-culture in Section II of the Yoga-Sutras is progressive in character it follows that the purpose of these three elements in II-l is of a more preliminary nature than that in II-32. Their purpose in II-32 is the same as that of the other elements of Niyama and has been discussed at the proper place. What is the purpose in the context of II-l? Let us see. 

Anyone who is familiar with the goal of Yogic life and the kind of effort it involves for its attainment will realize that it is neither possible nor advisable for anybody who is absorbed in the life of the world and completely under the influence of Klesas to plunge all at once into the regular practice of Yoga. If he is sufficiently interested in the Yogic philosophy and wants to enter the path which leads to its goal he should first accustom himself to discipline, should acquire the necessary knowledge of the Dharma-Sastras and especially of the Yoga-Sastras and should reduce the intensity of his egoism and all the other Klesas which are derived from it. The difference between the outlook and the life of the ordinary worldly man and the life which the Yogi is required to live is so great that a sudden change from the one to the other is not possible and if attempted may produce a violent reaction in the mind of the aspirant, throwing him back with still greater force into the life of the world. A preparatory period of self-training in which he gradually assimilates the Yogic philosophy and its technique and accustoms himself to self-discipline makes the transition from the one life to the other easier and safer. It also incidentally enables the mere student to find out whether he is sufficiently keen to adopt the Yogic life and make a serious attempt to realize the Yogic ideal. There are too many cases of enthusiastic aspirants who for no apparent reason cool off, or finding the Yogic discipline too irksome, give it up. They are not yet ready for the Yogic life.

Even where there is present the required earnestness and the determination to tread the path of Yoga it is necessary to establish a permanent mood and habit of pursuing its ideal. Mere wishing or willing is not enough. All the mental powers and desires of the Sadhaka should be polarized and aligned with the Yogic ideal. Many aspirants have very confused and sometimes totally wrong ideas with regard to the object and technique of Yoga. Many of them have very exaggerated notions with regard to their earnestness and capacity to tread the path of Yoga. Their ideas become clarified and their capacity and earnestness are tested severely in trying to practise Kriya-Yoga. They either emerge from the preliminary self-discipline with a clearly defined aim and a determination and capacity to pursue it to the end with vigour and single-minded devotion, or they gradually realize that they are not yet ready for the practice of Yoga and decide to tune their aspiration to the lower key of mere intellectual study.

This preparatory self-discipline is triple in its nature corresponding to the triple nature of a human being. Tapas is related to his will, Svadhyaya to the intellect and Isvara-Pranidhana to the emotions. This discipline, therefore, tests and develops all the three aspects of his nature and produces an all-round and balanced growth of the individuality which is so essential for the attainment of any high ideal. This point will become clear when we consider the significance of these three elements of Kriya-Yoga in dealing with II-32.

There exists some confusion with regard to the meaning of the Samskrta word Kriya, some commentators preferring to translate it as ‘preliminary’, others as ‘practical’. As a matter of fact Kriya-Yoga is both practical and preliminary. It is preliminary because it has to be taken up in the initial stages of the practice of Yoga and it is practical because it puts to a practical test the aspirations and earnestness of the Sadhaka and develops in him the capacity to begin the practice of Yoga as distinguished from its mere theoretical study however deep this might be.

Burning zeal in practice, self-study and study of scriptures, and surrender to God are the acts of yoga.

Iyengar Commentary:

For Patañjali, the practice of yoga is the ‘yoga of action’, kriyayoga, composed of tapas, self-discipline, svadhyaya, self-study and Isvara pranidhana, surrender to God.

Tapas is the blazing desire to burn away the impurities of body, senses and mind. Svadhyaya is the repetition of sacred mantras and the study of spiritual sacred texts in order to comprehend one’s own self. Isvara pranidhana is surrender of one’s body, mind and soul to God through love for Him.
Most commentators consider that this pada is intended for novices, and not for those who have already reached a high level of spiritual evolution. This is surely untrue, as sadhana is meant for both. The argument that it is only for those still roaming aimlessly in the world of pleasure does not take account of the fact that this wandering is merely a sign of a fluctuating consciousness, which may remain a problem even for evolved souls. By following the precepts of kriyayoga, all aspirants may learn to live in unshakeable serenity regardless of circumstances.

From this pada onwards, both beginner and evolved soul learn how to stabilize the mind. Its instructions enable the evolved soul to progress more rapidly towards the goal of purity and emancipation.

The disciplines of purifying man’s three constituents, body, speech and mind constitute kriyayoga, the path to perfection. Our bodies are purified by self-discipline (tapas), our words by Self-study (svadhyaya) and our minds by love and surrender to Him (Isvara pranidhana).

This sutra represents the three great paths: karma, jñana and bhakti. The path of action (karma-marga) is the discipline (tapas) of body, senses and mind. The path of knowledge (jnana-marga) is the study of the self (svadhyaya) from the skin to the core and back again. The path of love of God (bhakti-marga) is surrender (pranidhana) of all to God.

Sadhana pada identifies the source of all these paths. The first represents life, the second wisdom. The third, through the surrender of ego, brings the humility that leads to the effulgent, sorrowless light of Isvara, God.
”

Excerpt From
Light on the Yoga Sutras of Patanjali
B. K. S. Iyengar
https://books.apple.com/us/book/light-on-the-yoga-sutras-of-patanjali/id538108384
This material may be protected by copyright.

Accepting pain as help for purification, study of spiritual books and surrender to the Supreme Being constitute Yoga in practice.

Satchidananda Commentary:

Using the Sanskrit terms, Kriyā Yoga comprises tapas, svādhyāya and Īśvara praṇidhāna. Tapas is often misunderstood, because it gets translated as “mortification” or “austerity, ” when it actually stands for something different here. Tapas means “to burn or create heat.” Anything burned out will be purified. The more you fire gold, for example, the more pure it becomes. Each time it goes into the fire, more impurities are removed.

But how can this burning process be effected with our mental impurities? By accepting all the pain that comes to us, even though the nature of the mind is to run after pleasure. We will actually be happy to receive pain if we keep in mind its purifying effects. Such acceptance makes the mind steady and strong because, although it is easy to give pain to others, it is hard to accept without returning it. Such self-discipline obviously cannot be practiced in our meditation rooms, but only in our daily lives as we relate with other people.

Tapas also refers to self-discipline. Normally the mind is like a wild horse tied to a chariot. Imagine the body is the chariot; the intelligence is the charioteer; the mind is the reins; and the horses are the senses. The Self, or true you, is the passenger. If the horses are allowed to gallop without reins and charioteer, the journey will not be safe for the passenger. Although control of the senses and organs often seems to bring pain in the beginning, it eventually ends in happiness. If tapas is understood in this light, we will look forward to pain; we will even thank people who cause it, since they are giving us the opportunity to steady our minds and burn out impurities.

In the seventeenth chapter of the Bhagavad Gītā, Lord Kṛṣṇa [Krishna] talks about tapasya. He says, “Those who practice severe austerities not enjoined by the scriptures; who are given to hypocrisy and egoism, impelled by the forces of lust and attachment; who are senseless; who torture all the elements in the body and Me also who dwells in the body; know thou these to be of demoniacal resolves.” In the name of tapasya people sometimes practice all sorts of self-torture. In the East there are sādhus (ascetics) who lie on beds of nails or keep one arm raised in the air so the arm gets thinner and thinner and finally decays. These are all just forms of self-torture. Lord Kṛṣṇa himself says these people are demons because they disturb the pure Self who dwells within their bodies. Self-discipline is an aid to spiritual progress, whereas self-torture is an obstacle.

Lord Kṛṣṇa divides the true austerities into three groups: physical, verbal and mental. He classifies worship, purity, straightforwardness, celibacy and non-injury as the austerities of the body. Many people immediately come to the conclusion that physical tapasya is not suitable for them. The moment they hear the word “celibacy” they become dismayed. But brahmacarya, or celibacy, means control, not suppression, of the sex desire or sex force. If the mind can be filled with sublime thoughts by meditation, mantra repetition, prayer, study of scriptures and contemplation of the sexless, pure Self, the sex desire will be devitalized by the withdrawal of the mind. On the other hand, suppression of sexual desire will attach you to it again and again, producing wet dreams, irritability and mental restlessness. So the mind should be purified first; then it is easy to control the senses. Strict control over the senses alone will lead to difficulties instead of spiritual progress.

The next tapas is austerity of speech. Speech should bring tranquility and be truthful, pleasant and beneficial. As the Vedic teaching goes, “Satyam bruvat priyam bruvat.” “Speak what is true, speak what is pleasant.” And one should not speak what is true if it is not pleasant, nor what is pleasant if it is false. If something is true and unpleasant, we should make it more pleasant by presenting it in a proper way. And mental austerity is described by Śrī Kṛṣṇa as serenity of mind, goodheartedness, self-control and purity of nature.

Next comes svādhyāya, or study. This means study that concerns the true Self, not merely analyzing the emotions and mind as the psychologists and psychiatrists do. Anything that will elevate your mind and remind you of your true Self should be studied: the Bhagavad Gītā, the Bible, the Koran, these Yoga Sūtras or any uplifting scripture. Study does not just mean passing over the pages. It means trying to understand every word— studying with the heart. The more often you read them, the more you understand. For thousands of years, so many people have been studying the Bible. Every day, thousands of people read this same book. On the other hand, we have millions and millions of books that, after we read them once, we throw away as trash. We don’t exhaust the Bible even after reading it hundreds of times. Each time we read it we see it in a new light. That is the greatness of the holy scriptures. They are that way because they were created by holy prophets who experienced the truth. Each time we read these works we elevate ourselves to see a little more.

It is something like going to the Empire State Building. When you look out of a first floor window you see something. From the second floor, you see a little more; from the third floor, still more. But when you finally reach the hundred and first floor and look over the balcony, you see something completely different.

Similarly, in reading the scriptures, we slowly rise up, expanding and enlarging the mind. The more we elevate the mind, the better our understanding is. But only when we become prophets ourselves will we fully understand the scriptures. That is nature’s law. If you want to understand me fully, you must become me. Otherwise, you can understand me only according to your own capacity. In the same way, God cannot be understood by books alone. God can only be understood when you become God. A Tamil proverb says, “Only a saint knows a saint. Only a snake knows the leg of another snake.” You cannot exactly understand how a snake crawls unless you become a snake. We can hear things, study, form our own opinions, use our imagination, but nothing can equal experience.

Many people simply become walking libraries. They have thousands of books recorded in their brains like computers, but that doesn’t mean they have actually experienced the Self. The Self cannot be known by theory alone. By merely thinking, no one has ever understood the One that is beyond the mind. Only when you transcend the mind can you understand it. This is where Yoga differs from most other psychological approaches. They usually believe you have to understand everything with the mind and that beyond it you cannot understand anything. They stop there, but Yoga claims there is a knowledge possible without the mind. All that you know through the mind is limited and conditioned. How is the limited mind to understand the Unlimited One? Only by transcending it and getting into the unlimited.

Study is all right—but not for mere logic, quoting or fighting. Actually, it is only when you “quote” from your own experience that your words have weight. Sri Ramakrishna Paramahamsa used to say, “Forget all you have learned; become a child again. Then it will be easy to realize that wisdom.” Sometimes, learning becomes an obstacle if you don’t know what and how much to learn. So, limit your reading and put into practice what you read. Just select one or two books—anything that will remind you of your goal.

The last part of Kriyā Yoga is simple but great. It is surrendering to the Supreme Being. I understand this to mean dedicating the fruits of your actions to God or to humanity—God in manifestation. Dedicate everything—your study, your japa, your practices—to God. When you offer such things, God accepts them but then gives them back many times magnified. You never lose what you have given. Even virtuous, meritorious deeds will bind you in some form or other if you do them with an egoistic feeling. Every time you do something, feel, “May this be dedicated to God.” If you constantly remember to do this, the mind will be free and tranquil. Try not to possess anything for yourself. Temporarily keep things but feel you are just a trustee, not an owner.

Be like the mother who receives a soul, nourishes it for nine months and then lets it come out into the world. If the mother were always to keep the baby in her womb, what would happen? There would be great pain. Once something has ripened, it should be passed on. So dedication is true Yoga. Say, “I am Thine. All is Thine. Thy will be done.” Mine binds; Thine liberates. If you drop “mines” all over, they will “undermine” your life—or blow up in your face. But if you change all the “mines” to Thines, you will always be safe.

Let us all dedicate our lives for the sake of the entire humanity. With every minute, every breath, every atom of our bodies we should repeat this mantra: “dedication, dedication, giving, giving, loving, loving.” That is the best japa, the best Yoga which will bring us all permanent peace and joy and keep the mind free from the disturbances of the citta vṛttis.

The Yogi whose Vrttis have thus become powerless (controlled) obtains in the receiver, receiving, and received (the self, the mind and external objects), concentratedness and sameness, like the crystal (before different coloured objects.)

Vivekananda Commentary:

What results from this constant meditation? We must remember how in a previous aphorism Patanjali went into the various states of meditation, and how the first will be the gross, and the second the fine objects, and from them the advance is to still finer objects of meditation, and how, in all these meditations, which are only of the first degree, not very high ones, we get as a result that we can meditate as easily on the fine as on the grosser objects. Here the Yogi sees the three things, the receiver, the received, and the receiving, corresponding to the Soul, the object, and the mind. There are three objects of meditation given us. Firs the gross things, as bodies, or material objects, second fine things, as the mind, the Chitta, and third the Purasa qualified, not the Purasa itself, but the egoism. By practice, the Yogi gets established in all these meditations. Whenever he meditates he can keep out all other thought; he becomes identified with that on which he mediates; when he meditates he is like a piece of crystal; before flowers the crystal becomes almost identified with flowers. If the flower is red, the crystal looks red, or if the flower is blue, the crystal looks blue.

“ Now,” — This word here denotes undertaking. A text giving a revised critical teaching of Yoga is to be understood as having been undertaken.

Yoga is contemplation (Samadhi, trance), and it is a characteristic of the mind pervading all its planes. The planes of the mind are : —

Wandering (Ksipta) ; Forgetful (Mudha) ; Occasionally steady or distracted (Viksipta) ; One-pointed (Ekagra) ; and Restrained (Niruddha).

Of these the contemplation in the occasionally steady mind does not fall under the heading of Yoga, because of unsteadiness appearing in close sequence. That however, which in the one-pointed mind, fully shows forth an object existing as such in its most perfect form, removes the afflictions, loosens the bonds of karma and thus inclines it towards restraint, is said to be the Cognitive Trance <f?ainprajh6ta Samfidhi). And we shall explain further that this is accompanied by philosophical curiosity (vitarka), meditation (vichara), bliss (Amanda), and egoism (asmita).

When however all the modifications come under restraint, the trance is ultra-cognitive (Asamprajnata Samadhi).

~ Rāma Prasāda translation.