From Sahih Bukhari (Hadith 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
Reference: Bukhari 82