Musnad Abu Ya'la al-Mawsili 115:248

Zuhayr narrated to us, Abd al-Samad narrated to us, Hammam narrated to us, Qatadah narrated to us, from Anas ibn Malik: He narrated to them that a Jewish person passed by the Messenger of Allah, may Allah bless him and grant him peace, and said, "As-samu 'alaykum" (Death be upon you). The companions of the Messenger of Allah, may Allah bless him and grant him peace, responded to him. The Prophet, may Allah bless him and grant him peace, said, "He only said, 'As-samu 'alaykum'." So he called him, and he confessed. The Prophet, may Allah bless him and grant him peace, said, "Respond to him as he said."