with salām, for salām entails honoring the person and supplicating for him; when you say, “Peace be upon you,” you are supplicating for him. This, however, is merely a welcome and a greeting.
It should be said: If they treat us in this manner, then we may treat them likewise; or if there is some benefit in doing so, such as winning their hearts, then we may do so; or if it is out of fear of their harm, then we may do so. For example, if you work in a company whose manager is a disbeliever, and you enter to discuss some matter concerning the company without greeting him, he may harbor ill feeling toward you and perhaps harm you. But if you say, “How are you this morning?” or “How are you?” this removes the rancor from his heart and protects you from his harm. This does not fall under the Prophet’s prohibition against initiating salām to them.
If they greet us with salām, then we must reply to them, as indicated by the Quran and the Sunnah. But should we reply by saying, “And upon you,” or should we respond with the same greeting they gave?
The answer is: The greeting they offer us will be one of three types: either they clearly say, “Peace be upon you”; or they clearly say, “Death be upon you”; or they say something unclear, neither pronouncing the letter lām distinctly nor omitting it in an unmistakable manner. If they clearly say, “Peace be upon you,” as is now found among the non-Muslims living among us, who explicitly say, “Peace be upon you”—because their tongues are non-Arabic and they learn the greeting by rote, so you find one of them saying it plainly—then we may reply to them by saying, “Peace be upon you too,” or we may say, “And upon you.” If they clearly say, “Death be upon you,” then we say, “Death be upon you,” or, more preferably, we say, “And upon you.” The evidence for this is that a man