Ibn Hibbaan narrated in his Saheeh (493) from Abu Hurayrah (may Allaah be pleased with him) that a man passed by the Messenger of Allaah (peace and blessings of Allaah be upon him) when he was in a gathering and said, “Salaamun ‘alaykum.” He (the Prophet (peace and blessings of Allaah be upon him)) said, “Ten hasanahs.” Another man passed by and said, “Salaamun ‘alaykum wa rahmat-Allaahi (Peace be upon you and the mercy of Allaah).” He said, “Twenty hasanahs.” Then another man passed by and said, “Salaamun ‘alaykum wa rahmat-Allaahi wa barakaatuhu (Peace be upon you and the mercy of Allaah and His blessings).” He said: “Thirty hasanahs.” A man got up and left the gathering and did not say salaam. The Prophet (peace and blessings of Allaah be upon him) said, “How soon your companion has forgotten. When one of you comes to a gathering and says salaam, if he wants to sit down then let him do so. Then when he wants to leave, let him say salaam, for the one is not more important than the other.” Classed as saheeh by al-Albaani in Saheeh al-Targheeb wa’l-Tarheeb, 2712.