The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fada'il Al-Sahabah)
Muslim :: Book 31 : Hadith 6091
Abu Musa reported: I was in the company of Allah's Apostle (may peace be upon him) as he had been sitting in Ji'rana (a place) between Mecca and Medina and Bilal was also there, that there came to Allah's Apostle (may peace be upon him) a desert Arab, and he said: Muhammad, fulfill your promise that you made with me. Allah's Messenger (may peace be upon him) said to him: Accept glad tidings. Thereupon the desert Arab said: You shower glad tidings upon me very much; then Allah's Messenger (may peace be upon him) turned towards Abu Musa and Bilal seemingly in a state of annoyance and said: Verily he has rejected glad tidings but you two should accept them. We said: Allah's Messenger, we have readily accepted them. Then Allah's Messenger (may peace be upon him) called for a cup of water and washed his hands in that and face too and put the saliva in it and then said: Drink out of it and pour it over your faces and over your chest and gladden yourselves. They took hold of the cup and did as Allah's Messenger (may peace be upon him) had commanded them to do. Thereupon Umm Salama called from behind the veil: Spare some water in your vessel for your mother also, and they also gave some water which had been spared for her.