Majma al-Zawaid — Hadith 10057

Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) said: "I saw in a dream that I was wearing a strong coat of armour, and I saw a cow being slaughtered. I interpreted the strong coat of armour as Madinah, and the cow as some people; and Allah is the One who brings good." The narrator says: He said to his companions: "If we stay in Madinah and they enter upon us in it, we will fight them." The people said: "By Allah, O Messenger of Allah! They never entered upon us in our city in the days of ignorance (Jahiliyyah), so how can they come to us in Islam?" The Prophet (peace and blessings be upon him) said: "Then do as you wish!" Then the Prophet (peace and blessings be upon him) put on his armour. The Ansar said (to one another): "Have we not rejected the opinion of the Messenger of Allah?" Then they came and said: "O Prophet of Allah! Do as you see fit." The Prophet (peace and blessings be upon him) said: "It is not proper for a prophet, once he has put on his armour, to take it off before fighting."
Ahmad recorded it, and its narrators are the narrators of the Sahih.