Sahih Bukhari Volume 9, Book 87, Hadith Number 135.

Narrated By ‘Abdullah bin ‘Umar : Allah’s Apostle said, “While I was sleeping, I was given a bowl full of milk (in the dream) and I drank from it (to my fill) till I noticed its wetness coming out of my limbs. Then I gave the rest of it to ‘Umar bin Al-Khattab.” The persons sitting around him, asked, “What have you interpreted (about the dream) O Allah’s Apostle?” He said, “(It is religious) knowledge.”