Al-Fath 48:16

قُل لِّلۡمُخَلَّفِينَ مِنَ ٱلۡأَعۡرَابِ سَتُدۡعَوۡنَ إِلَىٰ قَوۡمٍ أُوْلِي بَأۡسٖ شَدِيدٖ تُقَٰتِلُونَهُمۡ أَوۡ يُسۡلِمُونَۖ فَإِن تُطِيعُواْ يُؤۡتِكُمُ ٱللَّهُ أَجۡرًا حَسَنٗاۖ وَإِن تَتَوَلَّوۡاْ كَمَا تَوَلَّيۡتُم مِّن قَبۡلُ يُعَذِّبۡكُمۡ عَذَابًا أَلِيمٗا 16

Say to those who remained behind of the bedouins, "You will be called to [face] a people of great military might; you may fight them, or they will submit. So if you obey, Allah will give you a good reward; but if you turn away as you turned away before, He will punish you with a painful punishment