Read Surah Al-Fath 48:16: "Say unto those bedouin who stayed behind: “In time you will be called upon [to fight] against people of great prowess in..." Full Arabic text, English translation, and image generator.
قُلْ لِلْمُخَلَّفِينَ مِنَ الْأَعْرَابِ سَتُدْعَوْنَ إِلَىٰ قَوْمٍ أُولِي بَأْسٍ شَدِيدٍ تُقَاتِلُونَهُمْ أَوْ يُسْلِمُونَ ۖ فَإِنْ تُطِيعُوا يُؤْتِكُمُ اللَّهُ أَجْرًا حَسَنًا ۖ وَإِنْ تَتَوَلَّوْا كَمَا تَوَلَّيْتُمْ مِنْ قَبْلُ يُعَذِّبْكُمْ عَذَابًا أَلِيمًا
Say unto those bedouin who stayed behind: “In time you will be called upon [to fight] against people of great prowess in war: you will have to fight against them [until you die] or they surrender. And then, if you heed [that call], God will bestow on you a goodly reward; but if you turn away as you turned away this time, He will chastise you with grievous chastisement.”