Narrated 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."
USC-MSA web (English) reference: Vol. 6, Book 60, Hadith 489
Arabic reference: Book 65, Hadith 4965