Musnad Abu Ya'la al-Mawsili 115:273

Zuhayr narrated to us, Yunus ibn Muhammad narrated to us, Shayban narrated to us, from Qatadah, from Anas, that a Jew came to the Prophet, may Allah bless him and grant him peace, and said, "As-samu 'alaykum" (Death be upon you). The people responded to him. The Prophet of Allah, may Allah bless him and grant him peace, said, "Do you know what he said?" They said, "Allah and His Messenger know best. He greeted you, O Prophet of Allah." He said, "No, but he said such and such. Bring him back to me." So they brought him back to him. He said, "Did you say, 'As-samu 'alaykum'?" He said, "Yes." The Prophet of Allah, may Allah bless him and grant him peace, said at that, "If one of the People of the Book greets you, then say, 'Wa 'alaykum' (And upon you)." He said, "Upon you is what you said." They came to you and greeted you with a greeting with which Allah did not greet you.