Narrated Ibn 'Umar:

Allah's Apostle 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 asked, "What have you interpreted (about this dream)? "O Allah's Apostle ,!" he replied, "(It is religious) knowledge."

حَدَّثَنَا سَعِيدُ بْنُ عُفَيْرٍ، قَالَ حَدَّثَنِي اللَّيْثُ، قَالَ حَدَّثَنِي عُقَيْلٌ، عَنِ ابْنِ شِهَابٍ، عَنْ حَمْزَةَ بْنِ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ ابْنَ عُمَرَ، قَالَ سَمِعْتُ رَسُولَ اللَّهِ ﷺ قَالَ " بَيْنَا أَنَا نَائِمٌ أُتِيتُ بِقَدَحِ لَبَنٍ، فَشَرِبْتُ حَتَّى إِنِّي لأَرَى الرِّيَّ يَخْرُجُ فِي أَظْفَارِي، ثُمَّ أَعْطَيْتُ فَضْلِي عُمَرَ بْنَ الْخَطَّابِ ". قَالُوا فَمَا أَوَّلْتَهُ يَا رَسُولَ اللَّهِ قَالَ " الْعِلْمَ ".