It is narrated from Sayyiduna Anas (may Allah be pleased with him), he said that a Jew passed by the Prophet (peace and blessings be upon him) and said: «السام علیکم» (May death be upon you). The Companions replied to the greeting, so the Prophet (peace and blessings be upon him) said: "He has said «السام علیکم» ." The Jew was caught and he admitted it. The Prophet (peace and blessings be upon him) said: "You should also reply to him in the same way."