Originally Posted by Jakebeth

Does he have contact with anyone in Israel from whom it would be easy to ask for a letter of explanation for his visit?

I haven't tried a letter of this kind specifically, but I know anecdotally that if the government has some kind of assurance from an Israeli citizen that your visit is legitimate, that can help smooth things. My mildly-informed opinion based on different experiences also says that a nice, brief letter in Hebrew would be ideal.