وَلَمَّا سُقِطَ فِىٓ أَيْدِيهِمْ وَرَأَوْا۟ أَنَّهُمْ قَدْ ضَلُّوا۟ قَالُوا۟ لَئِن لَّمْ يَرْحَمْنَا رَبُّنَا وَيَغْفِرْ لَنَا لَنَكُونَنَّ مِنَ ٱلْخَـٰسِرِينَ Qur’an Al-A'raf (7:149)Walamm a suqi t a fee aydeehim waraaw annahum qad d alloo q a loo lain lam yar h amn a rabbun a wayaghfir lan a lanakoonanna mina alkh a sireen a
Lit., "when it was made to fall upon their hands" - an idiomatic phrase denoting intense remorse, probably derived from the striking ("falling") of hand upon hand as an expression of grief or regret.
The whole of verse {149} is a parenthetic clause (jumlah mu'taridah) referring to a later time - for the repentance of the Israelites came after Moses' return from Mount Sinai, of which the next verse speaks.