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."
Hadith Referenceسنن دارمي / من كتاب الرويا / 2196
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):إسناده صحيح على شرط مسلم، [مكتبه الشامله نمبر: 2205]
Hadith Takhrijاس روایت کی سند صحیح على شرط مسلم ہے۔ دیکھئے: [أحمد 351/3] ، [نسائي فى الكبرىٰ 7647]
Brief Explanation
(Commentary on Hadith 2195)
Like the aforementioned dream, this dream is also related to the Battle of Uhud, in which the Messenger of Allah (sallallahu alayhi wa sallam) first saw that the sword broke and then was restored, and a cow was slaughtered.
The breaking of the sword referred to the Muslims being afflicted with hardship and becoming scattered during the Battle of Uhud; then all gathered together and drove away the disbelievers and polytheists.
The slaughtering of the cow was an indication towards the martyrdom of some of the noble Companions (radi Allahu anhum). From these ahadith, it is understood that the breaking of the sword is a sign of calamity, and its restoration to its previous state is equivalent to the situation returning to normal, while the slaughtering of the cow is a sign of martyrdom and death.