Does a Muslim return the salam to a disbeliever if he greets him, or does he suffice with saying “And upon you”?

Question:
And upon you. Your Eminence, the father, the questioner says: If a Jew initiates with me saying, “As-salamu alaykum wa rahmatullahi wa barakatuh,” should I return the full greeting, or do I suffice with “Alaykum”?

Answer:
This is how the Prophet (peace and blessings be upon him) guided. He said: If the Jews and Christians greet you, say “Alaykum” and do not say “Alaykum as-salam wa rahmatullahi wa barakatuh.” Say “Alaykum.” Yes. Do not initiate the salam with the Jews and Christians. If they greet you, say “Alaykum.” Yes. Excellent.