Sahih Bukhari Volume 9, Book 87, Hadith Number 154.

Narrated By ‘Abdullah bin ‘Umar : I heard Allah’s Apostle saying, “While I was sleeping, I saw a bowl full of milk was brought to me and I drank of it (to my fill) till I noticed its wetness flowing (in my body). Then I gave the remaining of it to ‘Umar.” They asked, “O Allah’s Apostle! What have you interpreted (about the dream)? He said, “(It is Religious) knowledge.” (See Hadith No. 134)