Dealing with Apostates 
Bukhari :: Book 9 :: Volume 84 :: Hadith 62
Narrated Ibn 'Umar:
Allah's Apostle said, "When the Jews greet anyone of you they say: 'Sam'Alaika (death be upon you); so you should say; 'Wa 'Alaika (and upon you).'"
Dealing with Apostates
Bukhari :: Book 9 :: Volume 84 :: Hadith 62
Narrated Ibn 'Umar:
Allah's Apostle said, "When the Jews greet anyone of you they say: 'Sam'Alaika (death be upon you); so you should say; 'Wa 'Alaika (and upon you).'"