It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When any of you comes to a gathering, he should say salam (greet with peace), and when he gets up to leave, he should also say salam. Surely, the latter is not more important than the former."
Through another chain, it is also narrated in a similar manner, marfu‘an, from Sayyiduna Abu Hurairah (may Allah be pleased with him).
Hadith Referenceالادب المفرد / كتاب السلام / 1007
Hadith Gradingالألبانی:صحيح
Hadith Takhrij«صحيح : سنن أبى داؤد ، الأدب ، ح : 5208 و جامع الترمذي ، ح : 2706»