Maliks Muwatta Book 53, Hadith Number 3.

Section : Greeting Jews and Christians.

Yahya related to me from Malik from Abdullah ibn Dinar that Abdullah ibn Umar said that the Messenger of Allah, may Allah bless him and grant him peace, said, “When a jew greets you, and says ‘Death to you’ (as-samu alaykum) say, ‘And to you.'”

Yahya said, “Malik was asked whether a person who greeted a jew or christian, should apologise for it. He said, ‘No’.”