While I was asleep I saw (in a dream) a cup containing milk being 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: Messenger of Allah: How do you interpret it? He said: This implies knowledge. (Using translation from Muslim 2391a)
كَانَ رَسُولُ اللهِ ﷺ يُحَدِّثُ يَقُولُ «بَيْنَا أَنَا نَائِمٌ رَأَيْتُنِي أُتِيتُ بِقَدَحٍ فَشَرِبْتُ مِنْهُ حَتَّى إِنِّي لَأَرَى الرِّيَّ يَجْرِي فِي أَظْفَارِي ثُمَّ أَعْطَيْتُ فَضْلِي عُمَرَ بْنَ الْخَطَّابِ» قَالُوا فَمَا ذَلِكَ يَا رَسُولَ اللهِ؟ قَالَ «الْعِلْمُ»