It was narrated that ‘Abdullah (رضي الله عنه) said:

We used not to know what to say in the prayer, we would say: Peace be upon Allah, peace be upon Jibreel, peace be upon Mika’eel. Then the Messenger of Allah (ﷺ) taught us and said: “Verily Allah is as-Salam, so when you sit after two rak'ahs, say: 'All compliments, prayers and pure words are due to Allah. Peace be upon you, O Prophet (ﷺ), and the mercy of Allah and His blessings. Peace be upon us, and on the righteous slaves of Allah" - Abu Wa'il said in his hadeeth from ‘Abdullah from the Prophet (ﷺ): “for if you say that, it will reach every righteous slave in heaven and on earth." And Abu Ishaq said in the hadeeth of ‘Abdullah from the Prophet (ﷺ): "If you say that, it will reach every angel who is close to Allah or every Prophet who was sent or every righteous slave - ‘l bear witness that there is no god but Allah, and I bear witness that Muhammad is His slave and Messenger."’