Number disagreement between subject and verb in Shakespeare?

I guess this is a quote from Shakespeare's Macbeth:

Come what come may, Time and the hour runs through the roughest day.

I'm confused about the subject-verb agreement in both sentences.

1. AFAIK in the first sentence "what come may" (or "what may come") is the subject, and the first word "come" is the verb. But does the verb have to be singular if the subject is a clause?


2. In the second sentence the subject is of the form "A and B", but why is the verb singular instead of plural here?

Sorry if the question sounds silly; I'm not a native speaker of English.