سُنَّةَ اللَّهِ الَّتِي قَدْ خَلَتْ مِن قَبْلُ ۖ وَلَن تَجِدَ لِسُنَّةِ اللَّهِ تَبْدِيلًا
“[This is] Allah's way, already long established [in the past]. And you will find no change in Allah's way.”
This ayah is part of Surah al-Fath, revealed -- as this event's own significance note states -- "concerning this incident" (Q48:1), the Treaty of Hudaybiyyah.