Bukhari Collection: ::Book Number 9:: Hadith # 61
Narrated `Aisha:A group of Jews asked permission to visit the Prophet (and when they were admitted) they said, "As-Samu 'Alaika (Death be upon you)." I said (to them), "But death and the curse of Allah be upon you!" The Prophet said, "O `Aisha! Allah is kind and lenient and likes that one should be kind and lenient in all matters." I said, "Haven't you heard what they said?" He said, "I said (to them), 'Wa 'Alaikum (and upon you).