Narrated `Abdullah bin `Umar: I heard Allah's Messenger (ﷺ) saying, "While I was sleeping, I saw a bowl full of milk was brought to me and I drank of it (to my fill) till I noticed its wetness flowing (in my body). Then I gave the remaining of it to `Umar." They asked, "O Allah's Messenger! What have you interpreted (about the dream)? He said, "(It is Religious) knowledge." (See Hadith No. 134)
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، أَخْبَرَنِي حَمْزَةُ بْنُ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " بَيْنَا أَنَا نَائِمٌ أُتِيتُ بِقَدَحِ لَبَنٍ فَشَرِبْتُ مِنْهُ، حَتَّى إِنِّي لأَرَى الرِّيَّ يَجْرِي، ثُمَّ أَعْطَيْتُ فَضْلَهُ عُمَرَ ". قَالُوا فَمَا أَوَّلْتَهُ يَا رَسُولَ اللَّهِ قَالَ " الْعِلْمُ ".
sunnah.com