Sahih Bukhari · Hadith 5016
Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) - كتاب التفسير
حدثنا آدم، حدثنا شيبان، حدثنا قتادة، عن أنس رضى الله عنه قال لما عرج بالنبي صلى الله عليه وسلم إلى السماء قال " أتيت على نهر حافتاه قباب اللؤلؤ مجوفا فقلت ما هذا يا جبريل قال هذا الكوثر ".
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.'
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).