Sahih Bukhari Volume 8, Book 75, Hadith Number 371.

Narated By Abu Humaid As-Saidi : The people said, “O Allah’s Apostle ! How may we send Salat on you?” He said, “Say: Allahumma Salli ‘ala- Muhammadin wa azwajihi wa dhurriyyatihi kama sal-laita ‘ala ali Ibrahim; wa barik ‘ala Muhammadin wa azwajihi wa dhurriyyatihi kamabarakta ‘ala ali Ibrahim innaka hamidun majid.”