Sahih Muslim Book 26, Hadith Number 5384.

Chapter : Prohibition of saying first as-Salam-u-Alaikum to the people of the book, and how their salutations should be responded.

‘Aisha reported that a group of Jews came to Allah’s Messenger (may peace be upon him) and sought his audience and said: As-Sam-u-‘Alaikum. ‘Aisha said in response: As-Sim-u-‘Alaikum (death be upon you) and curse also, whereupon Allah’s Messenger (may peace be upon him) said: ‘Aisha, verily Allah lose kindness in every matter. She said: Did you bear what they said? Thereupon he said: Did you not hear that I said (to them): Wa ‘Alaikum.