Al-Bara'at / At-Taubah (Repentance)
Surah 9 · Verse 122
And it is not (proper) for the believers that they should go out all together (to fight), so why not a group go out from every party among them, so that (those who remain behind) could develop sound understanding in religion and (through this religious knowledge) warn their people when they return to them (from war) so that they (too) could be cautious. (R 15)
If all the male members go out to fight, elderly men, women and children will be left unguarded. Besides, in any country men are involved in the supply of essential services like, water, electricity, food etc., therefore some men will have to remain in the city. Those who go out will be engaged in fighting but those who remain at home can find time to acquire knowledge of Islam and pass it on to their brotheren when they return from war.
