ثُمَّ عَفَوْنَا عَنكُم مِّن بَعْدِ ذَٰلِكَ لَعَلَّكُمْ تَشْكُرُونَ
Summa 'afawnaa 'ankum mim ba'di zaalika la'allakum tashkuroon
Then, even after that, we pardoned you, so that you might be grateful.
ʿAfw, the word for this pardon, means to efface or wipe out, and Arabic distinguishes it from maghfira, which covers a thing over without removing it. So the pardon named here erases rather than conceals, which is why the closing purpose is gratitude rather than relief. The offence it answers was described one verse earlier in the plainest terms the passage uses.