The Book of Drinks (Kitab Al-Ashriba)
Muslim :: Book 23 : Hadith 5070
'Abdullah b. Busr reported: AUah's Messenger (may peace be upon him) came to my father and we brought to him a meal and a preparation from dates, cheese and butter. He ate out of that. He was then given dates which he ate but he placed their stones between his fingers, and he joined his forefinger and middle finger. Shu'ba reported: I think that this hadith God's willing also contains (these words): Putting of date stones between two fingers. Then a drink was brought for him and he drank it, and then gave it to one who was on his right side. He (the narrator) said: My father took hold of the rein of his riding animal and requested him to supplicate for us. Thereupon he said: O Allah. bless them in what Thou hast provided them as a sustenance; and forgive them and have mercy upon them.