Sahih Muslim Book 26, Hadith Number 5388.

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

Jabir b. Abdullah reported that some people from amongst the Jews said to Allah’s Messenger (may peace be upon him) Abu’l-Qasim. as-Sam-u-‘Alaikum, whereupon he said: Wa ‘Alaikum, ‘Aisha was enraged and asked him (Allah’s Apostle) whether he had not heard what they had said. He said, I did hear and I retorted to them (and the curse that I invoked upon them would receive response from Allah), but (the curse that they invoked upon us) would not be responded.