Sayyiduna Abdullah bin Mas’ud (may Allah be pleased with him) narrated that when we (in the early days of Islam) used to pray with the Prophet Muhammad (peace and blessings be upon him), we would say: Peace be upon Allah before His servants, peace be upon Jibreel, peace be upon Mika’il, peace be upon so-and-so. Then (once), when the Messenger of Allah (peace and blessings be upon him) finished the prayer, he turned towards us and said: Allah Himself is Peace, so when any of you sits in prayer, he should say:“All greetings, prayers, and pure words are for Allah. 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.”Because when he recites this supplication, it will reach every righteous servant in the heavens and the earth.“I bear witness that there is no god but Allah, and I bear witness that Muhammad is His servant and Messenger.”After this, he has the choice to recite whatever supplication he wishes, but this is after reciting the Salat (blessings) upon the Prophet.