Qur'an 48:16

قُل لِّلْمُخَلَّفِينَ مِنَ ٱلْأَعْرَابِ سَتُدْعَوْنَ إِلَىٰ قَوْمٍ أُو۟لِى بَأْسٍ شَدِيدٍ تُقَـٰتِلُونَهُمْ أَوْ يُسْلِمُونَ ۖ فَإِن تُطِيعُوا۟ يُؤْتِكُمُ ٱللَّهُ أَجْرًا حَسَنًا ۖ وَإِن تَتَوَلَّوْا۟ كَمَا تَوَلَّيْتُم مِّن قَبْلُ يُعَذِّبْكُمْ عَذَابًا أَلِيمًا

Say unto those of the wandering Arabs who were left behind: Ye will be called against a folk of mighty prowess, to fight them until they surrender; and if ye obey, Allah will give you a fair reward; but if ye turn away as ye did turn away before, He will punish you with a painful doom.