9:122
۞ وَمَا كَانَ ٱلْمُؤْمِنُونَ لِيَنفِرُوا۟ كَآفَّةً ۚ فَلَوْلَا نَفَرَ مِن كُلِّ فِرْقَةٍ مِّنْهُمْ طَآئِفَةٌ لِّيَتَفَقَّهُوا۟ فِى ٱلدِّينِ وَلِيُنذِرُوا۟ قَوْمَهُمْ إِذَا رَجَعُوٓا۟ إِلَيْهِمْ لَعَلَّهُمْ يَحْذَرُونَ
9:122
And it is not (proper) for the believers to go out to fight (Jihad) all together. Of every troop of them, a party only should go forth, that they (who are left behind) may get instructions in (Islamic) religion, and that they may warn their people when they return to them, so that they may beware (of evil). - Muhammad Taqi-ud-Din al-Hilali and Muhammad Muhsin Khan (English)