Silsilah as-Sahihah 2641 — Etiquette of Salam

It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Noble Prophet (peace and blessings of Allah be upon him) said: "The younger should greet the elder, the one who is walking should greet the one who is sitting, and those who are few in number should greet those who are greater in number."