أَوْ يُغْنِي عَنْكَ نَدَمُكَ إِذَا زَلَّتْ قَدَمُكَ؟
Or will your remorse avail you once your foot has slipped?
Yughnī ʿanka means “be of use to you”; nadam is regret; zallat qadamuka depicts a foot slipping, here figuratively suggesting a grave mistake or decisive fall.
The warning does not deny the value of timely remorse. It distinguishes repentance while action remains possible from regret after the chance for correction has passed.