Galatians 1:1

In these verses we have the preface or introduction to the epistle, where observe, I. The person or persons from whom this epistle is sent - from Paul an apostle, etc., and all the brethren that were with him. 1. The epistle is sent from Paul; he only was the penman of it. And, because there were some among the Galatians who endeavoured to lessen his character and authority, in the front of it he gives a general account both of his office and of the manner in which he was called to it, which afterwards, in this and the following chapter, he enlarges more upon. As to his office, he was an apostle. He is not afraid to style himself so, though his enemies would scarcely allow him this title: and, to let them see that he did not assume this character without just ground, he acquaints them how he was called to this dignity and office, and assures them that his commission to it was wholly divine, for he was an apostle, not of man, neither by man; he had not the common call of an ordinary minister, but an extraordinary call from heaven to this office.

— Matthew Henry's Concise Commentary (public domain)