New answers tagged social-convention
You could call him "cousin". That could be a nice way to emphasize the relationship between Jews and Muslims as descendents of Abraham. "Friend" would also be appropriate. I'm not exactly sure about Muslim protocol, but for Jews, it is not necessary to use a word for him, and as havarka says, you could simply call him by his first name or Mr. Last Name, ...
Maybe "reb" or "rebbe" rather than "rabbi"? That's more along the lines of "wise man" without the formal clerical connotations.
what about his name?! That sounds like appropriate! or Believer!
Can you call him "achi"? That means "my brother" in Hebrew. I don't know if that would be acceptable under your religious beliefs (as it isn't in Arabic), but that might work. You could also consider calling him "yedidi" which means my friend in Hebrew. Or you might try "gadol" which can mean something along the lines of "big man" or significant ...
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