Sahih al Bukhari 82

Narrated Ibn `Umar:Allah's Messenger (ﷺ) said, "While I was sleeping, I saw that a cup full of milk was brought to me and I drank my fill till I noticed (the milk) its wetness coming out of my nails. Then I gave the remaining milk to `Umar Ibn Al-Khattab" The companions of the Prophet (ﷺ) asked, "What have you interpreted (about this dream)? "O Allah's Messenger (ﷺ) ,!" he replied, "(It is religious) knowledge

Sahih al Bukhari 82
Book 3, Hadith 24