It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) sent out a military expedition and appointed a Christian as their commander. He became angry with his army over some matter and said to them: "Did not the Messenger of Allah (peace and blessings be upon him) command you to obey me?" The companions replied: "Yes, he did." Then he said: "Gather firewood." Then he had a fire lit and said: "I give you a strict order to jump into this fire." Some people actually intended to enter the fire, but then a young man among them said: "You came to the Messenger of Allah (peace and blessings be upon him) to save yourselves from the fire, so do not be hasty. First, meet the Noble Prophet (peace and blessings be upon him). If he commands you to enter the fire, then do so." So when they returned to the Noble Prophet (peace and blessings be upon him) and related the whole incident to him, he (peace and blessings be upon him) said to them: "If you had entered the fire, you would never have come out of it. Obedience is only in what is permissible."