Advaita Vedānta

These commentators read the verse against a specific worry raised in the chapter. The earlier verse said that uttering 'Om Tat Sat' can repair a deficiency in a faithful person's sacrifice. So one might object: then a faithless person's act could also be repaired by the same words, and faith would become useless. This verse answers that objection. The faithless act is 'asat' and stands wholly outside the path that leads to the Lord, so the holy syllables cannot make it good; the repair works only where faith is already present. For these readers 'asat' means the unreal, that which lies outside the path to the Supreme, and the upshot is that the faithful person of sattva, even one untrained in scripture, can by faith and by the name of Brahman reach realization, while the faithless cannot. One of them adds that atheism (the settled conviction that there is no afterlife or God) is exactly what makes action fruitless and must by all means be shunned, and reads the address 'Partha' as Krishna gently telling his cousin not to fall into such a stance.

Śaṅkarācārya · Śrī Ānandagiri · Madhusūdana Sarasvatī · Dhanapati Sūri

Viśiṣṭādvaita

These commentators keep the reading spare and centered on faith itself. Even a scripturally correct oblation, gift, or austerity, if done without faith, is 'asat', because it is neither for liberation nor for any transmigratory fruit, neither hereafter nor here. One of them develops the point that 'asat' (non-being) is the exact opposite of 'Sat': the faithless act has no real being, because it lacks the inner stance that would have given it standing. The outer form, though prescribed by scripture, is only the body that faith animates; without faith the body is dead, with faith it is alive. The candidate is to take this as the chapter's final word, that faith is everything and the outer form is its vehicle.

Rāmānujācārya · Vedānta Deśika

Dvaita

These commentators anchor the verse in a supporting scriptural text and read 'faith' in an explicitly theistic key. Faith here includes devotion to Brahman, that is, to the Supreme. They cite a Vedic supplement saying that action done without faith is fruitless, and that the gods call 'sat' the action that has Him for its aim. The words 'tat' and the rest (the sacred designations) bring Brahman to bear on the act by their nearness, because the act then carries His form and is, as it were, an image of Him; through the Lord's being pleased the act becomes 'sat'. By contrast, an act with no aim at the Supreme and no faith is barren.

Madhvācārya · Śrī Jayatīrtha

Śuddhādvaita

For these commentators the missing ingredient is specifically the bond to the Lord. The faith whose absence makes an act 'asat' is the faith born of scripture that frames the act within relation to Bhagavan. One of them is careful to say the verse does not condemn faith as such; it condemns faith cut from the Lord. The very acts that the chapter promised the highest fruit are named 'asat' here when offered without the relation to the Lord the chapter has been teaching. The closing thrust is that three-guna action, even when done with faith, is finally fruitless, while the action beyond the gunas, sealed in 'Om Tat Sat' and aimed at the Lord, is fruitful; that alone is what the devotee is to do. The address 'Partha, my devotee' is held precisely against the harshness of the word 'asat', as a sign that the seeker is being guided, not merely scolded.

Vallabhācārya · Śrī Puruṣottama

Bhakti

These commentators read the verse as the tightest knot tying off the chapter, and stress that faith is the one base on which everything else rests. One says the whole long teaching of threefold faith, worship, food, sacrifice, austerity, gift, and the compensating triple name all rest on this single ground: where faith itself is absent, none of the rest can hold. Another spells out the emptiness vividly: even what is offered is as good as not offered, even what is given is as good as not given. One puts it that one should abandon the faith born of one's own nature and resort to the faith born of scripture to become fit for the highest good. The Marathi commentator piles up images for the futility: crores of sacrifices, oceans of charity, austerities held for thousands of years, all done without faith are like rain fallen on rock, oblations poured on ash, embracing a shadow, or slapping the sky; they bring not enjoyment but poverty and worry in both worlds.

Śrīdhara Svāmī · Śrīla Viśvanātha · Śrīla Baladeva · Sant Jñāneśvar

Kashmir Shaivism

This commentator frames the faithless person's act as 'tamasic' and in every way fruitless, yielding only the toil produced by assembling the various factors of the action; so one should never be a person without faith. 'Asat' is glossed simply as 'not commendable'. He adds a distinctive note of ease and grace: for those who strive in commendable action, welfare comes about easily. His summary verse observes that the very same entering of the factors and the same outward action, undistinguished in form, nonetheless issues in the goal of release for those possessed of clear knowledge, so the difference lies not in the outer act but in the inner clarity and faith behind it.

Ācārya Abhinavagupta

Modern

These commentators draw out the practical and psychological side. One explains 'asat' carefully as that which changes form and has no permanent existence, not sheer non-existence, and says acts done without faith, under pressure, to avoid trouble, or to gratify a craving yield no lasting fruit; he warns that lack of faith hardens the heart into ego and obstinacy, so that even hundreds of sacrifices or worldwide charity without faith and self-surrender are wasted energy, money, and time. Another reads the verse through the lens of desireless duty: the canon 'Om Tat Sat' covers all action done without craving for fruit, as duty, with pure intention and according to scripture; all other action is futile, which proves that action itself is never to be abandoned, only the hope of fruit. A third gives a probing analysis: the faithless person still performs scriptural rites, but only to be honored by society, to look good; such acts are 'asat' and bear no fruit here, hereafter, or in any future birth. He distinguishes this from sinful acts, which bind not by mere faithlessness but by attachment (raga); the merely faithless good act simply yields nothing, and that very lack of fruit, since the act was good in itself, is the doer's punishment. His conclusion is that in attaining the Supreme the act is never chief; faith and inner disposition are chief, so even the smallest plain act done selflessly for the Supreme becomes 'sat'.

Swami Sivananda · Lokmanya Tilak · Swami Ramsukhdas