Sura al-Fatḥ 48:16

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

qul lil-mukhallafīna mina l-aʿrābi sa-tudʿawna ilā qawmin ūlī baʾsin shadīdin tuqātilūnahum aw yuslimūna fa-in tuṭīʿū yuʾtikumu allāhu ajran ḥasanan wa-in tatawallaw ka-mā tawallaytum min qablu yuʿadhdhibkum ʿadhāban alīman

Say to the desert Arabs who lagged behind: "Ye shall be summoned (to fight) against a people given to vehement war: then shall ye fight, or they shall submit. Then if ye show obedience, Allah will grant you a goodly reward, but if ye turn back as ye did before, He will punish you with a grievous Penalty."