For I make known to you, brethren, the gospel, the one evangelized by me, that it is not according to man (Galatians 1:11).
The gospel Paul taught was not a message he received from men. He was taught this gospel by a revelation from Jesus Christ (Galatians 1:12).
When Saul was headed to Damascus to continue his persecution of “the way,” God redirected his path (Acts 9:2). Saul believed that those proclaiming the resurrection of Jesus were a sect that needed to be destroyed. After chasing most of the Christians out of Jerusalem, in his zeal, he expanded his search to Damascus. The name of the group he persecuted was “the way,” the early name for Christians (Acts 24:14; 1 Corinthians 15:9).
The experience on the Damascus road did not save Paul. His salvation, just like ours, came through grace (Galatians 1:15). As a saved Jew under the Mosaic law (Philippians 3:5–6), the truth of who Jesus is and therefore his death for sin and resurrection from the dead were revealed to Paul by Christ during his time in Arabia after this event on the Damascus road, converting him to Christianity (Galatians 1:17).
Thus, his gospel was not received from the apostles in Jerusalem or through any means of human making. Instead, it came directly from Christ. His gospel is a message of salvation by faith through grace and maturity, based on the truth of Christ’s death for sins and resurrection from the dead (1 Corinthians 15:1–4).