Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: People used to say: Peace be upon Allah, peace be upon Jibril, peace be upon the Messenger of Allah. Then the Messenger of Allah (peace and blessings be upon him) said: "Do not say: Peace be upon Allah, for Allah Himself is al-Salam. Rather, say: All verbal, physical and financial acts of worship are for Allah alone. 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 Allah, and I bear witness that Muhammad is the servant of Allah and His Messenger."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9857