لِّيَغْفِرَ لَكَ اللَّهُ مَا تَقَدَّمَ مِن ذَنبِكَ وَمَا تَأَخَّرَ وَيُتِمَّ نِعْمَتَهُ عَلَيْكَ وَيَهْدِيَكَ صِرَاطًا مُّسْتَقِيمًا
“So that Allah may forgive you for your past and future shortcomings, perfect His favor upon you, guide you along the Straight Path”
This is the specific, universally-attested asbab al-nuzul: Surah al-Fath (48:1-3) was revealed about the Hudaybiyyah treaty, quoted verbatim in the post.