Sunan an-Nasa'i, Volume 1, Book 5, Hadith 453 (DarusSalam) ⓘ

It was narrated from Anas bin Malik that the prayers were enjoined in Makkah, and that two angels came to the Messenger of Allah and took him to Zamzam, where they split open his stomach and took out his innards in a basin of gold, and washed them with Zamzam water, then they filled his heart with wisdom and knowledge.

أَخْبَرَنَا سُلَيْمَانُ بْنُ دَاوُدَ، عَنِ ابْنِ وَهْبٍ، قَالَ أَخْبَرَنِي عَمْرُو بْنُ الْحَارِثِ، أَنَّ عَبْدَ رَبِّهِ بْنَ سَعِيدٍ، حَدَّثَهُ أَنَّ الْبُنَانِيَّ حَدَّثَهُ عَنْ أَنَسِ بْنِ مَالِكٍ، أَنَّ الصَّلَوَاتِ، فُرِضَتْ بِمَكَّةَ وَأَنَّ مَلَكَيْنِ أَتَيَا رَسُولَ اللَّهِ صلى الله عليه وسلم فَذَهَبَا بِهِ إِلَى زَمْزَمَ فَشَقَّا بَطْنَهُ وَأَخْرَجَا حَشْوَهُ فِي طَسْتٍ مِنْ ذَهَبٍ فَغَسَلاَهُ بِمَاءِ زَمْزَمَ ثُمَّ كَبَسَا جَوْفَهُ حِكْمَةً وَعِلْمًا ‏.‏