But I make known to you, brethren, that the gospel which was preached by me is not according to man. 12 For I neither received it from man, nor was I taught it, but it came through the revelation of Jesus Christ.
13 For you have heard of my former conduct in Judaism, how I persecuted the church of God beyond measure and tried to destroy it. 14 And I advanced in Judaism beyond many of my contemporaries in my own nation, being more exceedingly zealous for the traditions of my fathers.
15 But when it pleased God, who separated me from my mother’s womb and called me through His grace, 16 to reveal His Son in me, that I might preach Him among the Gentiles, I did not immediately confer with flesh and blood, 17 nor did I go up to Jerusalem to those who were apostles before me; but I went to Arabia, and returned again to Damascus.
In authenticating his apostleship, Paul makes it quite clear that his call as an apostle has come from God — ‘through the revelation of Jesus Christ’. He refers back to God’s work of grace in his life, marked by an immediate desire to preach the gospel to the Gentiles. He did not immediately confer with anyone nor go up to Jerusalem to meet the other apostles, but went to Arabia and returned to Damascus.