siddhiḿ prāpto yathā brahma
tathāpnoti nibodha me
samāsenaiva kaunteya
niṣṭhā jñānasya yā parā

Translation of Bhagavad Gita 18.50

O son of Kunti, learn from Me how one who has achieved this perfection can attain to the supreme perfectional stage, Brahman, the stage of highest knowledge, by acting in the way I shall now summarize.

Commentary by Sri A.C. Bhaktivedanta Swami Prabhupada of Gaudiya Sampradaya:

The Lord describes for Arjuna how one can achieve the highest perfectional stage simply by being engaged in his occupational duty, performing that duty for the Supreme Personality of Godhead. One attains the supreme stage of Brahman simply by renouncing the result of his work for the satisfaction of the Supreme Lord. That is the process of self-realization. The actual perfection of knowledge is in attaining pure Krishna consciousness; that is described in the following verses.

Commentary by Sri Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

Understand by which method (yatha) one attains or realizes Brahman. This is the very highest stage of jnana (jnanasya nistha para). According to the Amara Kosa, nistha means consummation, final attainment.

The meaning is as follows: “Please understand the method by which, with the cessation of ignorance, and undertaking of the cessation of even knowledge (vidya), giving up even the process of jnana completely, a person will realize brahman.”

Commentary by Sri Ramanuja of Sri Sampradaya:

18.50 One who has attained ‘perfection’, viz., one who has attained perfection in meditation generated by the Karma Yoga performed day after day till death — how, in what way, he attains the brahman, learn this from Me in brief. It is the same Brahman who is described as the supreme consummation of knowledge. The meaning is that the self is the supreme consummation, the supreme end, of knowledge which is of the nature of meditation.

Commentary by Sri Sridhara Swami of Rudra Sampradaya:

The manner by which such renunciation attains the Brahman or spiritual substratum pervading all existence is by pristine spiritual knowledge. Lord Krishna is requesting to hear and learn from Him how this can be accomplished.

Commentary by Sri Madhvacharya of Brahma Sampradaya:

How and by what means perfection is reached and the consciousness of the brahman or spiritual substratum pervading all existence is achieved is given in the next three verses. This perfection is the epitome of spiritual wisdom.

Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

Now Lord Krishna in order to clearly establish that the Supreme state of highest devotion is the eternal cause of internal communion with the Supreme Lord explains the process. The Supreme Lord specifically emphasises that only by exclusive loving devotion to the Supreme Lord is highest devotion of the Supreme state achieved. This is the paramount goal and ultimate attainment and it is eternally transcendent and infinite in nature. In the Bhagavat Purana, Canto 11, chapter 13, verse 14 beginning etavan yoga adisto is stated: The yoga system taught by Lord Krishna’s devotees such as the Kumaras is withdrawing the mind from external objects and focusing it on the Supreme Lord. In the Visnu Purana the Prince Prahlad exclaims to the avatar or incarnation of Lord Krishna known as Narasinghadeva that: Just as the beloved has ardent love for the lover such is the depth of love that he wishes to have in his heart for the Supreme Lord.

Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

18.50 Nibodha, understand for certain; me, from Me, from My utterance-. Is it elaborately? The Lord says, no, samasena, in brief; eva, indeed, O son of Kunti, how siddhim praptah, one who has achieved success, one who, by worshipping God through one’s duties, has achieved success in the form of fitness of the body and organs for steadfastness in Knowledge, which comes from His grace; (-the reiteration of the phrase siddhim praptah is meant for introducing what follows; what is that succeeding subject for which this reiteration stands is being answered:) yatha tatha, that process by which, that process in the form of steadfastness in Knowledge, by which that process of acquiring steadfastness in Knowledge by which; apnoti, attains; brahma, Brahman, th supreme Self-. In order to point out-as ‘It is this’-the realization of Brahman which was promised in, ‘that process by which one…attains Brahman,’ the Lord says; ya, which; is the para, supreme; nistha, consummation, i.e. the supreme culmination; jnanasya, of Knowledge. Of what? Of the knowledge of Brahman. Of what kind is it? It is of the same kind as the realization of the Self. Of what kind is that? As is the Self. Of what nature is It? As has been described by the Lord and the Upanisadic texts, and established through reason. Objection: Is it not that knowledge takes the form of its object? But it is not admitted anywhere that the Self is an object, or even that It has form. Pseudo-Vedantin: Is it not heard of in such texts as, ‘radiant like the sun’ (Sv. 3.8), ‘Of the nature of effulgence’ (Ch. 3.14.2) and ‘Self-effulgent’ (Br. 4.3.9), that the Self has form? Objection: No, because those sentences are meant for refuting the idea that the Self is of the nature of darkness. When the Self is denied of possessing forms of substance, quality, etc., the contingency arises of the Self’s being of the nature of darkness. The sentences, ‘radiant like the sun,’ etc. are meant for rebuting this. And this follows from the specific denial of from by saying, ‘Formless’ (Ka. 1.3.15), and from such texts as, ‘His form does not exist within the range of vision; nobody sees Him with the eye’ (Ka. 2.3.9: Sv. 4.20), ‘soundless, touchless’ (ka. 1.3.15), etc. which show that the Self is not an object of perception. Therefore it remains unproved that there can be any knowledge which takes the form of the Self. How, then, can there be the knowledge of the Self? For, all knowledge that there can be with regard to objects assumes their respective forms. And it has been said that the Self has no form. Moreover, if both knowledge and the Self be formless, then how can there be the consummation [Firmness in Self-realization.] of the (repeated) contemplation on that (knowledge of the Self)? Vedantin: No. Since it can be established that the Self is supremely taintless, pure and subtle, and it can also be established that the intellect can have taintlessness etc. like the Self, therefore it stands to reason that the intellect can take a form resembling the consciousness of the Self. The mind becomes impressed with the semblance of the intellect; the organs become impressed with the semblance of the mind; and the body becomes impressed with the semblance of hte organs. Hence it is that the idea of the body itself being the Self is held by ordinary people. The Lokayatikas (materialists), who hold that the body is identical with consciousness, say that a person is a body endowed with consciousness; so also there are others who say that the organs are identical with consciousness; there are others who say that the mind is identical with consciousness, and still others who say that the intellect is identical with consciousness. Some accept as the Self the Unmanifest [The inmost Ruler (antaryamin), possessing a semblance of Consciousness.], called the Undifferentiated, which is more internal than that (intellect) and is within the domain of (primordial) ignorance. Indeed, in every case, beginning from the intellect to the body, the cause of mis-conceived Selfhood is the semblance of the Consciousness that is the Self. Hence, knowledge about the Self is not a subject for injunction. What then? Only the eradication of the superimposition of name, form, etc., which are not the Self, is what has to be undertaken, but not the knowledge of the Self that is Consciousness. For it is the Self which is experienced as possessed of the forms of all the various objects that are superimposed (on It) through ignorance. It is evidently because of this that the Buddhists who uphold the view of (momentary) consciousness have concluded that there is no substance at all apart from (momentary) consciousness, and that it is not in need of any other valid proof since they hold that it is self-cognized. Therefore, what is to be undertaken is only the elimination of the superimposition on Brahman through ignorance, but no effort is needed for knowing Brahman (Consciousness), for It is quite self-evident! It is because the intellect is distracted by particular appearances of name and form imagined through ignorance that Brahman, even though self-evident, easily realizable, nearer than all else and identical with oneself, appears to be concealed, difficult to realize, very far and different, But to those whose intellect has become free from external appearances and who have obtained the grace of a teacher and serenity of mind, there is nothing more blissful, manifest, well known, easily realized and nearer to oneself than this Self. And thus it has been declared, ‘directly realizable, righteous,’ etc. (9.2). However, some wiseacres assert that the intellect cannot comprehend the entity called the Self since It is formless; hence, complete steadfastness in Knowledge is impossible. This is truly so for those who have not associated with a traditional line of teachers; who have not heard the Upanisads; whose intellects are too much engrossed with external objects; and who have not applied themselves diligently to the perfect means of knowledge. For those, on the other hand, who are the opposite of these, it is absolutely impossible to have the idea of reality with regard to empirical objects, which are within the realm of duality involving the knower and the known, because in their case there is no perception of any other thing apart from the Consciousness that is the Self. We have already said how this is certainly so and not otherwise. It has been stated by the Lord also, ‘That during which creatures keep awake, it is night to the seeing sage’ (2.69). Therefore, the cessation of the perception of differences in the form of external things is alone the cause of resting in the reality of the Self. For, that which is called the Self is never an object which is not well known, attainable, rejectable or acceptable to anyone at any time. Were that Self to be indeed not self-evident, all activities would become meaningless. [According to Ast. the latter portion of this sentence is: svarthah sarvah pravrttayah vyarthah prasajyeran, all activities meant for one’s own benefit would become meaningless.-Tr.]. For it cannot be imagined that they could be undertaken for unconscious objects like the body etc. Besides, it cannot be that pleasure is for pleasure’s sake, or that sorrow is for sorrow’s sake. Moreover, all empirical dealings are meant for culminating in the realization of the Self. [According to B.S. 3.4.26, ‘On the strength of the Upanisadic sanction of sacrifices etc. all religious activities as well are necessary…’, sacrifices etc. are meant for leading to the realization of the Self, without which they would become meaningless.] Therefore, just as for knowing one’s own body there is no need of any other (external) means of knowledge so also there is no need of any other means of knowledge, for the realization of the Self which is innermost (in relation to the body etc.). Hence it is established that steadfastness in the knowledge of the Self is a fact very well known to the discriminating people. Even to those who hold that knowledge is formless and not cognized by direct perception, cognition of an object is dependent on knowledge. Hence it has to be admitted that knowledge is as immediate as pleasure etc. And this follows also from the impossibility of a desire to know (knowledge). Had knowledge been not self-evident, it could have been sought for like any object of knowledge. And in that case, as [This is Ast.’s reading; others read tatha.-Tr.] a knower seeks to perceive through knowledge such objects of knowledge as pot etc., similarly the knower would have sought to perceive knowledge through another knowledge! But this is not the case. Therefore knowledge is quite self-revealing, and for the very same reason the knower also is self-revealed. Hence, effort is not needed for knowledge, but only for the removal of the notion of what is not-Self. [In place of anatma-buddhi-nivrttau, Ast. has ‘anatmani atma-buddhi-nivrttau, for the termination of thinking what is not the Self as the Self’.-Tr.] Consequently, steadfastness in Knowledge is easy of accomplishment. It is being stated how this supreme consummation of Knowledge is to be attained:

Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:

18.41-60 Brahmana – etc. upto avasopitat. Surely the intrinsic nature of the Brahmanas etc., does not voilate what has been difined (above) by way of classifying their duties. Therefore, as far as you are concerned, you have the intrinsic quality of the Ksatriya (warrior), and your nature i.e., intrinsic quality, does, without fail, assume the part of the inciter of yourself, even though you don’t like it. For, a person who acts simply being incited by that (natural condition), there is the strong bondage of the merit or demerit. Therefore, perform actions following the means of correct knowledge, taught by Me. In that case, the bondage would disappear. The intention of the principal sentence (statement of the entire passage under study) is to help to get this idea. The meaning of the subordinate sentences (statements) is evident. Briefly (verse 50) : in short. Knowledge : i.e. the one which has been explained earlier. Nistha conveys, avoiding verbal jugglary, the meaning ‘what has been determined’. He who is endowed with intellect totally pure etc. : All this has been almost explained already. Hence, no more trouble is taken [to comment upon it].

Sanskrit Shloka Without Transliteration Marks:

siddhiḿ prāpto yathā brahma
tathāpnoti nibodha me
samāsenaiva kaunteya
niṣṭhā jñānasya yā parā

Sanskrit to English Word for Word Meanings:

siddhim — perfection; prāptaḥ — achieving; yathā — as; brahma — the Supreme; tathā — so; āpnoti — one achieves; nibodha — try to understand; me — from Me; samāsena — summarily; eva — certainly; kaunteya — O son of Kuntī; niṣṭhā — the stage; jñānasya — of knowledge; yā — which; parā — transcendental.