Musannaf Ibn Abi Shayba 27:24

Ibn Fudayl narrated to us, from ‘Ata’ ibn al-Sa’ib, from Muharib ibn Dithar, from Ibn ‘Umar, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Al-Kawthar is a river in Paradise. Its banks are of gold, and its bed is of pearls and precious stones (yaqut). Its soil is more fragrant than musk, its water is sweeter than honey, and it is whiter than snow."