Anas narrated that the Messenger of Allah said:
"While I was traveling through Paradise, a river appeared before me whose banks had tents of pearl. I said to the angel: 'What is this?' He said: 'This is Al-Kauthar, which Allah has granted you.'" He said: "Then he put his hand in the clay, and removed musk from it, then I was raised up to Sidrat Al-Muntaha so I saw a magnificent light at it." (DE)
English reference (DE): Vol. 5, Book 44, Hadith 3360 (DE)
Arabic reference (DE): Book 47, Hadith 3685 (DE)