﴿ قُل لِّلْمُخَلَّفِينَ مِنَ ٱلْأَعْرَابِ سَتُدْعَوْنَ إِلَىٰ قَوْمٍ أُو۟لِى بَأْسٍۢ شَدِيدٍۢ تُقَٰتِلُونَهُمْ أَوْ يُسْلِمُونَ ۖ فَإِن تُطِيعُوا۟ يُؤْتِكُمُ ٱللَّهُ أَجْرًا حَسَنًۭا ۖ وَإِن تَتَوَلَّوْا۟ كَمَا تَوَلَّيْتُم مِّن قَبْلُ يُعَذِّبْكُمْ عَذَابًا أَلِيمًۭا ﴾

“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.””

Please check ayah 48:17 for complete tafsir.