Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Abdullah (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: "Salam is one of the names of Allah, which He has sent down to the earth, so spread it among yourselves. When a person greets people with Salam and they reply to him, then the one who initiated the Salam attains superiority over them, because he reminded them. And if they do not reply, then those (servants of Allah) who are better and purer than them respond to him."