When the Prophet ﷺ was taken up to the heavens, he said, "I came upon a river whose banks were domes of hollowed pearl.I asked, 'What is this, Jibreel?'He replied, 'This is al-Kawthar.'"
لما عرج بالنبي ﷺ إلى السماء قال: أتيت على نهر حافتاه قباب اللؤلؤ مجوفا. فقلت: ما هذا يا جبريل؟ قال: هذا الكوثر.
Bukhari narrated it in the tafsir (4964), from Adam, who said, Shayban told us, Qatada told us, from Anas, and he related it.Tirmidhi narrated it (3360), from Ahmad bin Mani, who said, Shurayh bin Numan told us, Hakam bin Abdul-Malik told us, from Qatada, from Anas, and he related the same, adding, "Then he reached out his hand into some clay and pulled out musk, then Sidrat Muntaha was raised up for me, and I saw a great light near it."Tirmidhi said, "Hasan sahih, and it has been narrated through more than one route from Anas."