قُل لِّلْمُخَلَّفِينَ مِنَ الْأَعْرَابِ سَتُدْعَوْنَ إِلَىٰ قَوْمٍ أُولِي بَأْسٍ شَدِيدٍ تُقَاتِلُونَهُمْ أَوْ يُسْلِمُونَ ۖ فَإِن تُطِيعُوا يُؤْتِكُمُ اللَّهُ أَجْرًا حَسَنًا ۖ وَإِن تَتَوَلَّوْا كَمَا تَوَلَّيْتُم مِّن قَبْلُ يُعَذِّبْكُمْ عَذَابًا أَلِيمًا
“Say to nomadic Arabs who stayed behind, "You will be called [to fight] against a people of great might who you will fight unless they submit. If you then obey, Allah will grant you a fine reward. But if you turn away as you did before, He will inflict upon you a painful punishment."”
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.