Hamza b. Abdullah b. 'Umar b. Khattab reported on the authority of his father that Allah's Messenger (ﷺ) said:
While I was asleep I saw (in a dream) a cup containing milk bein. presented to me. I took out of that until I perceived freshness being reflected through my nails. Then I presented the leftover to 'Umar b. Khattab. They said: Allah's Messenger: Fow do you interpret it? He said: This implies knowledge.