(Imām Bukhārī narrates): Abū Nu'aim narrated to us, he said: Al-A'mash narrated to us, from Shaqīq ibn Salamah, he said that 'Abdullāh ibn Mas'ūd, may Allāh be pleased with him, narrated that:

when we used to pray behind the Messenger of Allāh ﷺ, we used to say: "Al-salāmu 'alā Jibrīl wa Mīkā'īl" and "Al-salāmu 'alā fulān wa fulān." So the Messenger of Allāh ﷺ turned towards us and said: Allāh the Exalted is Himself al-Salām (Peace); so when any one of you prays, let him say: All verbal acts of worship are for Allāh, and all bodily acts of worship, and all financial acts of worship. O Prophet! Peace be upon you, and the mercy of Allāh, and His blessings. Peace be upon us, and upon the righteous servants of Allāh. So when you say this, this mercy will reach every righteous servant of Allāh in the heavens and the earth. (And say:) I bear witness that there is no god worthy of worship except Allāh, and I bear witness that Muhammad is the servant of Allāh and His Messenger.