Yahya related to me from Malik from Nuaym ibn Abdullah al-Mujmirthat Muhammad ibn Abdullah ibn Zayd told him that Abu Masud alAnsari said, "The Messenger of Allah, may Allah bless him and granthim peace, came to us at the gathering of Sad ibn Ubada. Bashir ibnSad said to him, 'Allah has ordered us to ask for blessings on you,Messenger of Allah. How should we do it?' The Messenger of Allah, mayAllah bless him and grant him peace, remained silent until we wishedwe had not asked him. Then he told us to say, 'O Allah, bless Muhammadand the family of Muhammad as You blessed Ibrahim, and give baraka toMuhammad and the family of Muhammad as You gave baraka to the familyof Ibrahim. In all the worlds You are worthy of Praise and Glorious,'and then give the taslim as you have learnt."Allahumma salliala Muhammad wa ali Muhammad kama sallaita Ibrahim, wa baraka alaMuhammad wa ali Muhammad kama baraktaala ali Ibrahim. Fi'l alamin,innaka Hamidu'm - Majid.
USC-MSA web (English) reference: Book 9, Hadith 70
Arabic reference: Book 9, Hadith 401