The reward for a person who spreads Salaam will be Jannah.
Narrated by Abu Yusuf Abdullah ibn Salam: “The Prophet (salAllaahu ‘alayhi wa sallam) said, “O people spread the Salaam, give food, offer night prayer when the people are asleep and you will enter Paradise in peace” “- Al-Tirmidhi, Hadith 849
These are easy for those whom Allah has mercy on. Spread the Salaam to everyone regardless if you know them or don’t.
Spreading the Salaam is also one of the means of attaining forgiveness. It is the best act in Islam.
The Prophet was asked, “What is the best act in Islam” He said, “To give food and to salute everyone whether you know or don’t know them”
Excellence of Greeting on Arrival and Departure:
Narrated by Abu Hurairah (radia Allaahu ‘anhu the Messenger of Allah said, “When one of you arrives he should say Salaam Alaikum and sit and he should do the same when he intends to leave” Abu Dawud
If you want to leave you have to say As-Salaam Alaikum. One time the Prophet was giving a sermon to the companions and he said this hadith. When he said that a man got up and left without saying the Salaam. He said, “How quickly he forgot!”
This is a Sunnah and a command from the Prophet (salAllaahu ‘alayhi wa sallam). Obey Allah and His Messenger so that you may receive mercy. The more you hold fast to the Sunnah the more you will receive the mercy of Allaah.