"I certify to you" translates into modern English as "let me make this clear." Then, just as he had denied their claim that his was an inadequate apostleship, he begins to deny their claim of an inadequate source of his gospel. He says it was "not after men," that is, it did not have its source in men. (The proliferation of manmade gospels is something that cannot be stopped. It seems as if God allows it to happen so that we will discern the true from the false.) There is a way we can tell the source of a gospel. A reasonably well-read person can compare Paul's gospel with gospels that come from men, and Paul's agrees with the rest of the Bible.
Another thing is that gospels of men always elevate man at God's expense. Sometimes it is very subtle, but it can even be discerned right in the book of Galatians, once we understand that the people Paul is confronting were elevating themselves as worthy—because of their works—to be called of God. They were not empty of their human nature at all but filled with it! It came out in their proud boasts about how great their works were.
Paul always denigrated himself in favor of God. God and Jesus Christ are always the great Ones, while all the rest of us are lowly servants. This is a major point to comprehend.
John W. Ritenbaugh
The Covenants, Grace, and Law (Part 24)
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