Sayyiduna Samurah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) commanded us to greet those on our right side with salam and that we should reply to each other's salam. In the narration of Muhammad bin Yazid, it is mentioned that we should say salam to each other. In the narration of Ibrahim, there is an addition that Hammam says: that is, (say salam) during the prayer (when turning for salam).