If you send salaam upon the Messenger (salAllaahu alaiyhi wasallam) from the farthest ends of the Earth, your salaam will reach him, because Allaah has appointed angels who travel about the Earth, and if anyone sends salaams upon the Messenger  (salAllaahu alaiyhi wasallam), they convey that salaam to the Messenger  (salAllaahu alaiyhi wasallam). So if we say now, “O Allaah, send blessings and peace upon the Messenger of Allaah,” our salaam will be transmitted to him. In prayer we say, “Al-salaamu ‘alayka ayyuha’l-nabiyyu wa rahmat-Allaahi wa barakaatuhu (Peace be upon you, O Prophet, and the mercy of Allaah and His blessings),” and the salaam is transmitted to him…


Shaykh Ibn ‘Uthaymeen