It is narrated from Hazrat Anas bin Malik (may Allah be pleased with him) that a Jew greeted the Prophet (peace and blessings be upon him) by saying "As-Saam Alaik" (death be upon you). The Prophet (peace and blessings be upon him) said to the companions (may Allah be pleased with them), "Call him to me and ask him, did you say 'As-Saam Alaik'?" When he admitted it, the Prophet (peace and blessings be upon him) said (to his companions), "When any of the People of the Book greet you, just say 'Wa Alaik' (and upon you)."