Narrated Ibn 'Umar:

I heard Allah's Apostle saying, "While I was sleeping, I was given a bowl full of milk (in a dream), and I drank of it to my fill until I noticed its wetness coming out of my nails, and then I gave the rest of it to 'Umar." They (the people) asked, "What have you interpreted (about the dream)? O Allah's Apostle?" He said, "(It is Religious) knowledge."

حَدَّثَنَا عَبْدَانُ، أَخْبَرَنَا عَبْدُ اللَّهِ، أَخْبَرَنَا يُونُسُ، عَنِ الزُّهْرِيِّ، أَخْبَرَنِي حَمْزَةُ بْنُ عَبْدِ اللَّهِ، أَنَّ ابْنَ عُمَرَ، قَالَ سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ " بَيْنَا أَنَا نَائِمٌ أُتِيتُ بِقَدَحِ لَبَنٍ، فَشَرِبْتُ مِنْهُ، حَتَّى إِنِّي لأَرَى الرِّيَّ يَخْرُجُ مِنْ أَظْفَارِي، ثُمَّ أَعْطَيْتُ فَضْلِي ". يَعْنِي عُمَرَ. قَالُوا فَمَا أَوَّلْتَهُ يَا رَسُولَ اللَّهِ قَالَ " الْعِلْمَ ".