Narrated Ibn 'Umar:
"The Messenger of Allah (ﷺ) said: 'I saw that I was brought a cup of milk, so I drank from it, and I gave my leftover to 'Umar bin Al-Khattab.' They said: 'So what did you interpret it as O Messenger of Allah?' He said: '(It is) Knowledge.'" (RU)
English reference (RU): Vol. 1, Book 46, Hadith 3687 (RU)
Arabic reference (RU): Book 49, Hadith 4051 (RU)