Paul says the gospel he preached was “not man’s gospel.” He did not receive it from man or learn it from man, but “through a revelation of Jesus Christ” (Galatians 1:11–12).
In Galatians 1:11–12 Paul insists that the message he publicly announced did not originate from ordinary human sources. These lines come early in the letter, after Paul has already expressed alarm that the Galatians are turning to a “different” message (Galatians 1:6–9). Having warned about competing announcements, Paul begins to explain why his own message carries weight.
Paul is defending the origin and authority of the message he announced (the “gospel”). Explicitly, he says it was not sourced “according to man,” and he backs that up by denying two normal human pathways: he did not receive it from a person, and he was not taught it by instruction.
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with Galatians 1:11-12, then read the surrounding section so the answer stays connected to the passage's flow.
11But I make known to you, brothers, concerning the gospel which was preached by me, that it is not according to man.
12For neither did I receive it from man, nor was I taught it, but it came to me through revelation of Jesus Christ.