Sahih Bukhari Volume 5, Book 58, Hadith Number 164.

Narated By ‘Aisha : I did not feel jealous of any of the wives of the Prophet as much as I did of Khadija (although) she died before he married me, for I often heard him mentioning her, and Allah had told him to give her the good tidings that she would have a palace of Qasab (i.e. pipes of precious stones and pearls in Paradise), and whenever he slaughtered a sheep, he would send her women-friends a good share of it.