Sunan Ibn Majah, Chapter: The Chapters of Establishing the Prayer and the Sunnah Regarding Them

that they said: "O Messenger of Allah! We have been commanded to send peace and blessings upon you. How should we send peace and blessings upon you?" He said: "Say: Allahumma salli 'ala Muhammadin wa azwajihi wa dhurriyatihi, kama sallayta 'ala Ibrahim; wa barik 'ala Muhammadin wa azwajihi wa dhurriyatihi kama barakta 'ala ali Ibrahim fil-'alAmeen, innaka Hamidum Majid (O Allah, send Your grace, honour and mercy upon Muhammad (SAW) and his wives and offspring, as You sent Your grace, honour and mercy upon Ibrahim. O Allah, send Your blessings upon Muhammad (SAW) and his wives and offspring, as You sent Your blessings upon the family of Ibrahim among the nations, You are indeed Praiseworthy, Most Glorious)." (Sahih)