The Kural in life
Drop the tainted gain the same day.
Valluvar is uncompromising here. Even if a gain brings nothing but profit — no visible harm at all — if it came by swerving from fairness, let it go the very day it arrives. The benefit does not cancel the crookedness; the only right response to unjust gain is to be rid of it at once.
Parimelazhagar: profit does not make it clean.
Parimelazhagar reads the verse together with the one before: fair wealth gives good, and wealth got by swerving gives harm — even when it wears the look of profit. So 'though it gives only good' is said precisely because such gain does not really give good. The instruction 'that very day' is the measure of how dangerous it is to keep.
The bonus you should refuse.
A deal that profits you but quietly cheats a supplier, a result that helps you but came by bending a rule — Valluvar's counsel is not to enjoy it carefully but to give it up immediately. Waiting 'until it's convenient' is how tainted gains become permanent. The same-day rule exists because delay is how the crooked becomes normal.
Gain that came by unfair means must be let go at once, even if it profits.
Valluvar is uncompromising: even a gain that brings only profit, if it came by swerving from fairness, must be dropped the very day it arrives. Parimelazhagar (reading it with the prior verse): swerved gain really gives harm, not good — 'though it seems to give good' marks the illusion, and 'that very day' marks how dangerous it is to keep.
Refuse unjust gain immediately — don't wait for a convenient time.
If something profits you but came by bending what's fair, give it up the day you notice — not 'once it's convenient.' Delay is exactly how a tainted gain becomes a permanent one and how crookedness becomes your normal. The profit never cancels the wrong; only letting it go does.