صحيح مسلم Sahih Muslim كتاب الصلاة The Book of Prayers
باب حُجَّةِ مَنْ قَالَ الْبَسْمَلَةُ آيَةٌ مِنْ أَوَّلِ كُلِّ سُورَةٍ سِوَى بَرَاءَةَ:

Chapter: The Proof Of Those Who Say That The Bismillah Is A Verse At The Beginning Of Every Surah, Except Bara'ah (At-Tawbah)

1 hadith
Hadith 400
حَدَّثَنَا أَبُو كُرَيْبٍ مُحَمَّدُ بْنُ الْعَلَاءِ ، أَخْبَرَنَا ابْنُ فُضَيْلٍ ، عَنْ مُخْتَارِ بْنِ فُلْفُلٍ ، قَالَ : سَمِعْتُ أَنَسَ بْنَ مَالِكٍ ، يَقُولُ : أَغْفَى رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِغْفَاءَةً ، بِنَحْوِ حَدِيثِ ابْنِ مُسْهِرٍ ، غَيْرَ أَنَّهُ ، قَالَ : نَهْرٌ وَعَدَنِيهِ رَبِّي عَزَّ وَجَلَّ فِي الْجَنَّةِ عَلَيْهِ حَوْضٌ ، وَلَمْ يَذْكُرْ : آنِيَتُهُ عَدَدُ النُّجُومِ .
Mukhtar bin Fulful reported that he had heard Anas bin Malik (RA) say that the Messenger of Allah (ﷺ) dozed off, and the rest of the hadith is the same as transmitted by Mushir except for the words that he (the Holy Prophet) said: 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.
Hadith Reference Sahih Muslim / The Book of Prayers / Hadith: 400
Hadith Grading محدثین: أحاديث صحيح مسلم كلها صحيحة
Hadith Takhrij «أحاديث صحيح مسلم كلها صحيحة»