- Neither he nor his servants have left.
- Neither he nor his servants has left.
Which of these is correct? I think the first one is correct but my friend says it's the other one.
Though you likely know that grammatical rules are often violated, subject/verb agreement with either/or and neither/nor generally follows the rule below.
The verb in an either/or statement agrees with the noun that is closest to it.
So either of the following would be correct (though the first one sounds vastly better to my AmE ear.)
Neither he nor his servants have left.
Neither his servants nor he has left.