Muwatta Imam Malik (Riwayat Ibn al-Qasim)

It is narrated from Sayyiduna Abu Humayd As-Sa'idi (may Allah be pleased with him) that he said: O Messenger of Allah! How should we send blessings upon you? The Messenger of Allah (peace and blessings be upon him) said: "Say «اللهم صل على محمد وعلى أزواجه وذريته كماصليت على آل إبراهيم ، وبارك على محمد وأزواجه وذريته كماباركت على آل إبراهيم إنك حميد مجيد» O Allah! Send blessings upon Muhammad (peace be upon him), his wives, and his offspring as You sent blessings upon the family of Ibrahim. And send blessings upon Muhammad (peace be upon him), his wives, and his offspring as You sent blessings upon the family of Ibrahim. Surely, You are Praiseworthy and Glorious."