Musnad Ahmad 980:14

I read to Abd al-Rahman: Malik [narrated to us], and Ishaq narrated to us, Malik informed me, from Nu'aym ibn Abd Allah al-Mujmir, that Muhammad ibn Abd Allah ibn Zayd al-Ansari—in the hadith of Abd al-Rahman, and Abd Allah ibn Zayd is the one who was shown the call to prayer—informed him, from Abu Mas'ud al-Ansari, that he said: The Messenger of Allah (peace and blessings of Allah be upon him) came to us in the gathering of Sa'd ibn Ubadah. Bashir ibn Sa'd said to him: "Allah has commanded us to invoke blessings upon you, O Messenger of Allah, so how should we invoke blessings upon you?" He said: The Messenger of Allah (peace and blessings of Allah be upon him) remained silent until we wished that he had not asked him. Then he said: "Say: 'O Allah, send blessings upon Muhammad and upon the family of Muhammad, as You sent blessings upon Ibrahim, and bless Muhammad and the family of Muhammad, as You blessed the family of Ibrahim among the worlds; You are Praiseworthy, Glorious.' And the salutation is as you have already learned."