Sahih Muslim 400
Sahih Muslim · Book 4: The Book of Prayers · The Proof Of Those Who Say That The Bismillah Is A Verse At The Beginning Of Every Surah, Except Bara'ah (At-Tawbah)
Mukhtar b. Fulful reported that he had heard Anas b. Malik say that the Messenger of Allah (ﷺ) dozed off, and the rest of the hadith is the same as transmitted by Mus-hir except for the words that he (the Holy Prophet) said:
حَدَّثَنَا أَبُو كُرَيْبٍ، مُحَمَّدُ بْنُ الْعَلاَءِ أَخْبَرَنَا ابْنُ فُضَيْلٍ ، عَنْ مُخْتَارِ بْنِ فُلْفُلٍ ، قَالَ سَمِعْتُ أَنَسَ بْنَ مَالِكٍ ، يَقُولُ أَغْفَى رَسُولُ اللَّهِ صلى الله عليه وسلم إِغْفَاءَةً . بِنَحْوِ حَدِيثِ ابْنِ مُسْهِرٍ غَيْرَ أَنَّهُ قَالَ " نَهْرٌ وَعَدَنِيهِ رَبِّي عَزَّ وَجَلَّ فِي الْجَنَّةِ عَلَيْهِ حَوْضٌ " . وَلَمْ يَذْكُرْ " آنِيَتُهُ عَدَدُ النُّجُومِ " .
It (Kauthar) is a canal which my Lord the Exalted and the Glorious has promised me in Paradise. There is a tank over it, but he made no mention of the tumblers like the number of the stars.