Sahih Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Volume: 005 / Book Number: 059 / Hadith Number: 407
Narrated Abu Musa:
The Prophet said, "I saw in a dream that I moved a sword and its blade got broken, and that symbolized the casualties which the believers suffered on the day of Uhud. Then I moved it again, and it became as perfect as it had been, and that symbolized the Conquest (of Mecca) which Allah helped us to achieve, and the union of all the believers. I (also) saw cows in the dream, and what Allah does is always beneficial. Those cows appeared to symbolize the faithful believers (who were martyred) on the day of Uhud."