سنن أبي داود

Umm Salamah, wife of the Prophet (May peace be upon him) is reported to have said: The Messenger of Allah (May peace be upon him) said: You will have commanders some of whom you will approve and some of whom you will disapprove. He who expresses disapproval with his tongue (Abu Dawud said : This is Hisham’s version) is guiltless; and he who feels disapproval in his heart, is safe, but he who is pleased and follows them. He was asked; shall we not kill them, Messenger of Allah? Abu Dawud’s version has : Shall we not fight with them? He replied : No, so long as they pray.