Book 39, Hadith 57

It was narrated from Abu 'Adur-Rahman from Ali that:the Messenger of Allah sent an army and appointed a man in charge of them. He lit a fire and said: "Enter it." Some people wanted to enter it, and other said: "We are trying to keep away from it." They mentioned that to the Messenger of Allah, and he said to those who had wanted to enter if: "If you had entered it you would have stayed there until the Day of Resurrection." And he spoke good words to the others. And he said: "There is no obedience if it involves disobedience toward Allah. Rather obedience is only (required) in that which is good