Musnad Abu Ya'la al-Mawsili 152:14

Narrated to us Muhriz ibn 'Awn, narrated to us 'Ali ibn Mushir, from al-A'mash, from Shaqiq ibn Salamah, from Ibn Mas'ud, who said: We used to say, when we sat in the prayer, "Peace be upon Allah before His servants, peace be upon Gabriel, peace be upon Michael, peace be upon so-and-so." He said: So we would say, "His angels." The Messenger of Allah (peace and blessings of Allah be upon him) turned to us and said: "Indeed, Allah is the Peace (as-Salam). So when you sit, say: 'The greetings (at-tahiyyat) are for Allah, and the prayers (as-salawat), and the good things (at-tayyibat). Peace be upon you, O Prophet, and the mercy of Allah and His blessings. Peace be upon us and upon the righteous servants of Allah.' I bear witness that there is no god but He, and I bear witness that Muhammad is His servant and His messenger." Then let him choose whatever speech he wishes.