Narrated Buraidah:
from his father who said: Whenever the Messenger of Allah (ﷺ) dispatched a commander of an army he would exhort him personally; that he should have Taqwa of Allah, and regarding those of the Muslims who are with him; that he should be good to them. He would say: 'Fight in the Name of Allah and in Allah's curse. Fight those who disbelieve in Allah and fight, do not be treacherous, nor mutilate, nor kill a child.