Musnad Ahmad 1156:134

Yahya ibn Sa'id narrated to us, from Hisham, who said: Al-Hasan narrated to us, from Dabbah ibn Mihsan, from Umm Salamah, from the Prophet, peace and blessings of Allah be upon him, who said: "There will be commanders over you; you will recognize [some of their actions] and you will disapprove [of others]. Whoever disapproves [of them] is absolved, and whoever dislikes [them] is safe, but [the sin is upon] the one who approves and follows." They said: "O Messenger of Allah, shall we not fight them?" He said: "No, as long as they pray the prayer."