Sahih Bukhari
Prophetic Commentary on the Quran (Tafseer of the Prophet (PBUH))
Volume: 006 / Book Number: 060 / Hadith Number: 490
Narrated Abu Bishr:
Said bin Jubair said that Ibn 'Abbas said about Al-Kauthar. "That is the good which Allah has bestowed upon His Apostle." I said to Sa'id bin Jubair. "But the people claim that it is a river in Paradise." Said said, "The river in Paradise is part of the good which Allah has bestowed on His Apostle."