Surah At-Tawba Verse 122

۞ وَمَا كَانَ الْمُؤْمِنُونَ لِيَنفِرُوا كَافَّةً ۚ فَلَوْلَا نَفَرَ مِن كُلِّ فِرْقَةٍ مِّنْهُمْ طَائِفَةٌ لِّيَتَفَقَّهُوا فِي الدِّينِ وَلِيُنذِرُوا قَوْمَهُمْ إِذَا رَجَعُوا إِلَيْهِمْ لَعَلَّهُمْ يَحْذَرُونَ

Wa maa kaanal mu'minoona liyanfiroo kaaaffah; falaw laa nafara min kulli firqatim minhum taaa'ifatul liyatafaqqahoo fiddeeni wa liyunziroo qawmahum izaa raja'ooo ilaihim la'allahum yahzaroon

Translation / The Meaning

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 their people when they return to them that they might be cautious.