The deepest secret is told to the one who finds no fault.

Advaita Vedānta

The "this knowledge" is the knowledge of Brahman, the non-dual Self. It is right knowledge of identity, summed up in scriptural phrases such as "Vasudeva is all," "all this is the Self alone," "one only, without a second," "I am Brahman." This knowledge alone is the direct means of liberation, and nothing else is; meditation and the worship of duality do not by themselves end ignorance. Some of these commentators add that meditation still has a role, but only an indirect one: by purifying the inner organ it ripens into this very knowledge, and so leads to liberation gradually rather than directly. The 'tu' is read as marking knowledge off from meditation, and the chapter as turning from the Brahman-to-be-meditated to the Brahman-to-be-known.

Śaṅkarācārya · Śrī Ānandagiri · Madhusūdana Sarasvatī · Śrī Nīlakaṇṭha · Dhanapati Sūri

Advaita Vedānta

On the timing of release, several of these commentators stress that liberation here is immediate, available here and now, not deferred to a future world. The eighth chapter described going by the path of flame (the deva-yana) to a gradual liberation at the end of the cosmic age; lest one think release comes only that way, this chapter teaches a present, direct freedom for the knower. One commentator hears the future-tense "you shall be freed" almost as a present rescue: knowing this, the listener is already on the way out of bondage.

Śrī Nīlakaṇṭha · Dhanapati Sūri · Śaṅkarācārya

Viśiṣṭādvaita

The "this knowledge" is worship of the Lord taking the form of devotion (bhakti). The vijnana paired with it is the particular knowing of the manner and the goal of that worship. The whole chapter proclaims the Lord's own supremacy and greatness, his sovereignty even while present in human form, and the yoga whose very form is devotion. The qualification 'anasuyave' is read pointedly: the fit candidate is one who, hearing the Lord's measureless and unlike-all-else glory, does not let a jealous heart question those high claims but holds them to be just so. The phrase "knowledge with realization" picks up the very wording of an earlier verse, so this chapter continues and fulfills the worship of the Lord by the knowing devotee.

Yāmunācārya · Rāmānujācārya · Vedānta Deśika

Śuddhādvaita

The "this knowledge" is the knowledge of the Lord's own akshara-aishvarya, his imperishable majesty, and crucially the knowledge of the very form of bhakti itself, which is womb-laden with true devotion. What sets this teaching apart, on this reading, is the uncommon power of devotion to purify and uplift even those who have fallen far. The earlier teaching, framed by the fourfold division of worshippers, was secret; this teaching is the most secret because it is framed by the greatness of the devotion that is to be offered. The Pushtimarga (grace) frame is explicit: the address 'te' ("to you") and the very telling of the secret are themselves a gift of grace, given only into a hearing already turned by the Lord's grace toward him; the secret is spoken out of compassion and not to be told to all.

Vallabhācārya · Śrī Puruṣottama

Bhakti

The "this knowledge" must be explained as devotion itself, not the well-known Self-knowledge of the earlier chapters; here "knowledge" means sole and pure devotion, devotion that stands alone and does not depend, as knowledge does, on prior purification of the inner faculty. Some of these commentators argue this from the wider passage: the later qualifier "imperishable" and the going beyond the three gunas fit devotion, not knowledge (since knowledge is of the nature of sattva), and the word "dharma" further on means devotion too. Vijnana is read as contemplative worship, etymologically "that by which one knows distinctly," or as the glorifying activities of devotion. This chapter, and especially the ninth and tenth together, is held to be the very heart of the Gita. One voice in this group, in a tender expansion, has Krishna confess he sees no one else fit for the secret and pour it out like seed-grain sown only in prepared soil.

Śrīdhara Svāmī · Śrīla Viśvanātha · Śrīla Baladeva · Sant Jñāneśvar

Bhedabheda

On the timing of release, this commentator directly opposes the view that liberation can be had here and now in this very body. He reports the claim that, since the gradual path of light (arcir-adi) was taught only for certain meritorious persons, an immediate liberation is now being declared, and he rejects it: it is precisely by the path of light, having crossed beyond the sphere of transmigration, that liberation comes through separation from the subtle body. One is not liberated here, in this body; so the view that liberation is right here is contrary to established doctrine. He reads the 'tu' as carrying the sense of pre-eminence and praises the coming knowledge to generate faith.

Śrī Bhāskara

Kashmir Shaivism

This commentator is terse here. He singles out freedom from fault-finding (anasuyatva) as the chief cause in the handing-on of knowledge, making the disciple's non-carping heart the decisive condition for transmission, and takes "knowledge and discernment" as already explained before.

Ācārya Abhinavagupta

Modern

These voices read the verse as the threshold of the Gita's supreme disclosure but weigh its content differently. One frames it as the opening of an integral knowledge of the whole Godhead, who is at once the immutable Self, the Lord in the cosmos, and the Divine within man, a wisdom that must be lived and grown into and that requires faith, since the critical intellect that goes by outward facts cannot receive it. One identifies the king-knowledge here specifically with the path of devotion (bhaktimarga), holding that this stanza does not refer to the immutable imperceptible Brahman at all, and that bhakti is called the king of the mysterious Vidyas because it is actually realizable and easy to follow. One reads 'idam' as the knowledge of the Self, distinguishing jnana as theoretical Self-knowledge from the study of the Upanishads and vijnana as direct intuitive realization, and dwells at length on freedom from jealousy as an essential qualification. One, non-sectarian and devotional, treats the secret as the tattva Krishna holds in his own heart and stresses that it is told only where the listener has no fault-finding and is full of reverence; he ties this 'guhya-tamam' to the 'sarva-guhya-tamam' of the eighteenth chapter to show both passages teach one and the same thing.

Sri Aurobindo · Lokmanya Tilak · Swami Sivananda · Swami Ramsukhdas