Sahih Bukhari Volume 4, Book 56, Hadith Number 744.

Narated By Isma’il bin Abi Khalid : I heard Abii Juhaifa saying, “I saw the Prophet, and Al-Hasan bin ‘Ali resembled him.” I said to Abu- Juhaifa, “Describe him for me.” He said, “He was white and his beard was black with some white hair. He promised to give us 13 young she-camels, but he expired before we could get them.”