Even those who already sought freedom kept acting; so will you.

Read through the two-case instruction that divides by the doer's stage.

Once egoity and craving for fruit are absent, action cannot stain the one who acts, because the sense of being a separate doer has already dissolved. So the instruction divides in two. If you do not yet know the Self, act to purify your own mind, since that purification is what finally makes knowledge possible. If you already know it, act to hold the world together, so your own example does not mislead others into dropping duties still theirs to carry. The ancients acted in exactly this spirit, and so the precedent settles the matter for anyone reading after them.

Read through knowledge of the Lord as the specific ground of freedom.

Here the knowledge that frees is knowledge of the Lord himself, not an abstract Self-knowledge apart from him. The ancients, their sin shaken off by knowing Krishna as he has just disclosed himself, went on acting because of that very knowledge; and Arjuna, his own sin shaken off the same way, is told to do that very action. The ancients are named precisely, Vivasvat, Manu, and their line, so the precedent is a real genealogy, not a vague appeal to the past in general.

Read honestly, since the surviving comment here is thin.

What remains of the Dvaita comment on this verse is a short remark: it reads the passage as an example of conduct, tied to the word thus, with still earlier glossed simply as that which existed before. It would misrepresent the source to expand this into a full three-part argument about dependence and grace in Madhva's own confident voice. On a Dvaita reading generally, one might extend this to say that even the knowers among the ancients acted from longing for a still fuller release, rather than producing that release through the act itself; but that extension draws on the wider system, not on what this verse's brief remark actually says.

Read honestly, since only a single sentence of this comment survives.

The extant fragment is one line: therefore you too, purified by this understanding, do the actions that must necessarily be done. That is genuinely all there is to work with here, and it would be dishonest to present a fuller commentary as though it were his own extended words. What the fragment does show is a recognizable emphasis, purification of buddhi, understanding, and action named as necessary rather than optional, consistent with how this same reading treats other verses in the chapter. On a Kashmir Saiva reading, one would extend this further, that the ancients' action was freedom's own spontaneous expression rather than an imposed discipline, but that extension is clearly a modern inference, not the master's stated word on 4.15.

Read as a return to karma-yoga, with a precise purpose named for the ancients' action.

This verse is read as Krishna deliberately returning to the karma-yoga he was already teaching, after briefly setting aside the question of the Lord's impartiality. The ancient seekers acted in just this way for a specific purpose: purity of sattva, the clarifying of the inner instrument, rather than liberation as an immediate result of the act itself. The instruction to act, first, is read as marking a sequence: action comes first, and only afterward does fuller ripening, whether toward knowledge or toward devotion, actually unfold.

Read as a cumulative argument from precedent.

This reading draws out the logic of precedent with particular clarity: not just the ancients but the still-earlier ancients before them acted this way, so the argument is cumulative rather than resting on one example that might be dismissed as unusual. The weight of an unbroken lineage, generation reinforcing generation, is what finally makes the instruction to Arjuna feel settled rather than merely asserted.