Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh))

Bukhari :: Book 6 :: Volume 60 :: Hadith 488

Narrated Anas:

When the Prophet was made to ascend to the Heavens, he said (after his return), "I came upon a river the banks of which were made of tents of hollow pearls. I asked Gabriel. What is this (river?' He replied, 'This is the Kauthar.'