Sulayman ibn Buraydah reported on the authority of his father who said that when Allah’s Messenger (SAW) sent anyone as amir over an army, he instructed him, about himself, to fear Allah, and about the Muslims with him, to consider their welfare. He would (also) say, ‘Go ahead in jihad in the name of Allah and in the path of Allah. Fight those who disbelieve in Allah.’ Wage jihad. And do not be unfaithful about the booty, do not be unfaithful to your promise, do not mutilate and do not kill children.” And there is a narrative in the hadith.
[Muslim 1731, Abu Dawud 2612]