Sahih al-Bukhari 4964

Arabic

حَدَّثَنَا آدَمُ، حَدَّثَنَا شَيْبَانُ، حَدَّثَنَا قَتَادَةُ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ لَمَّا عُرِجَ بِالنَّبِيِّ صلى الله عليه وسلم إِلَى السَّمَاءِ قَالَ ‏ "‏ أَتَيْتُ عَلَى نَهَرٍ حَافَتَاهُ قِبَابُ اللُّؤْلُؤِ مُجَوَّفًا فَقُلْتُ مَا هَذَا يَا جِبْرِيلُ قَالَ هَذَا الْكَوْثَرُ ‏"‏‏.‏

English translation

Narrated Anas:When the Prophet (ﷺ) 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

Reference: Sahih al-Bukhari 4964, Book of Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)). English translation by Dr. Muhammad Muhsin Khan.