Sunan ad-Darimi

It is narrated from Sayyiduna Jabir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "I saw in a dream that I was in a well-protected coat of mail, and I saw cows being slaughtered. I interpreted this to mean that the coat of mail is Madinah, and the cows are a group of Muslims who will be martyred, and every matter of Allah is good. (And my opinion was) that if we remained in Madinah, when the polytheists attacked us, we would drive them away." The Ansar said: "By Allah, in the days of ignorance they could not enter our city, so will they be able to enter our neighborhoods after we have embraced Islam?" The Messenger of Allah (peace and blessings of Allah be upon him) said: "Then as you wish." So the people of the Ansar consulted and said that the opinion of the Messenger of Allah (peace and blessings of Allah be upon him) should be acted upon, and then they came to him and said: "O Messenger of Allah! Do as you see fit." The Messenger of Allah (peace and blessings of Allah be upon him) said: "Now you say this?" (At that time, he had already put on his armor, so) he said: "It does not befit any Prophet that when he has put on his armor, he should take it off without fighting."