۞ وَمَا كَانَ ٱلْمُؤْمِنُونَ لِيَنفِرُوا كَآفَّةً ۚ فَلَوْلَا نَفَرَ مِن كُلِّ فِرْقَةٍ مِّنْهُمْ طَآئِفَةٌ لِّيَتَفَقَّهُوا فِى ٱلدِّينِ وَلِيُنذِرُوا قَوْمَهُمْ إِذَا رَجَعُوٓا إِلَيْهِمْ لَعَلَّهُمْ يَحْذَرُونَ

Wama kana almu/minoonaliyanfiroo kaffatan falawla nafara min kullifirqatin minhum ta-ifatun liyatafaqqahoo fee addeeniwaliyunthiroo qawmahum itha rajaAAoo ilayhimlaAAallahum yahtharoon

And it is not for the believers to go forth [to battle] all at once. For there should separate from every division of them a group [remaining] to obtain understanding in the religion and warn [i.e., advise] their people when they return to them that they might be cautious.