Narrated `Abdullah bin `Umar:

I heard Allah's Messenger (ﷺ) saying, "While I was sleeping, I saw that a cup full of milk was brought to me and I drank of it and gave the remaining of it to `Umar bin Al-Khattab." They asked. What have you interpreted (about the dream)? O Allah's Messenger (ﷺ) ?" The Prophet (ﷺ) said. "(It is Religious) knowledge."

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، عَنْ حَمْزَةَ بْنِ عَبْدِ اللَّهِ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ ـ رضى الله عنهما ـ قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏"‏ بَيْنَا أَنَا نَائِمٌ أُتِيتُ بِقَدَحِ لَبَنٍ فَشَرِبْتُ مِنْهُ، ثُمَّ أَعْطَيْتُ فَضْلِي عُمَرَ بْنَ الْخَطَّابِ ‏"‏‏.‏ قَالُوا فَمَا أَوَّلْتَهُ يَا رَسُولَ اللَّهِ قَالَ ‏"‏ الْعِلْمَ ‏"‏‏.‏