Comma with Subjects and Verbs

A comma shouldn’t separate a subject from its verb. Separating the subject and its verb with a comma is a mistake generally made if the subject clause is long, and if the subject already has a verb in it (as part of a relative clause),

The things which cause me joy, may also cause me pain.

The subject of this sentence is the things which cause me joy, and its verb is may cause. Not only does this comma separate the verb from its subject, but the comma isn’t even required for clarity. We should definitely get rid of this comma.

The method of ensuring you are driving on the right route, is to check your G.P.S.

We don’t need a comma in this sentence, either.

Exception: The only time you may separate a subject from its verb is if the verb from the subject clause is repeated.

He who offends me, offends me greatly.

If we didn’t have the comma in this sentence, the reader might sound like a broken record. The slight pause emphasizes the repetition of the phrase.