The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 803
Abdullah b. Zaid-he who was shown the call (for prayer in a dream) narrated it on the authority of Mas'ad al-Ansiri who said: We were sitting in the company of Sa'id b. 'Ubida when the Messenger of Allah (may peace be upon him) came to us. Bashir b. S'ad said: Allah has commanded us to bless you. Messenger of Allah! But how should we bless you? He (the narrator) said: The Messenger of Allah (may peace be upon him) kept quiet (and we were so much perturbed over his silence) that we wished we had not asked him. The Messenger of Allah (may peace be upon him) then said: (For blessing me) say:" 0 Allah, bless Muhammad and the members of his household as Thou didst bless the mernbers of Ibrahim's household. Grant favours to Muhammad and the members of his household as Thou didst grant favours to the members of the household of Ibrahim in the world. Thou art indeed Praiseworthy and Glorious" ; and salutation as you know.