Sahih al-Bukhari 4965
صحيح البخاري#4965SahihNarrated Abu Ubaida:I asked `Aisha 'regarding the verse:--'Verily we have granted you the Kauthar.' She replied, "The Kauthar is a river which has been given to your Prophet on the banks of which there are (tents of) hollow pearls and its utensils are as numberless as the stars
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 65:487