Musnad Ahmad 1156:57

Yazid narrated to us, Hisham ibn Hassan narrated to us, from al-Hasan, from Dabbah ibn Mihsan, from Umm Salamah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There will be leaders over you, whose actions you will recognize and [others] you will disapprove of. Whoever disapproves [of them] is absolved, and whoever dislikes [their actions] is safe; but [the sin is upon] whoever is pleased and follows." They said: "O Messenger of Allah, shall we not fight them?" He said: "No, as long as they pray the five [daily prayers] for you."