BROTHERS and SISTERS, I proclaim to you that the Gospel which I preached is not of human origin, for I did not receive it from a human source, nor was I taught it, but I received it through a revelation of Jesus Christ. You have heard of my earlier life in Judaism, how I violently persecuted the Church of God and was trying to destroy it. I advanced in Judaism beyond many among my people of the same age, for I was far more zealous for the traditions of my ancestors. But when God, Who had set me apart before I was born and called me through His grace, was pleased to reveal His Son in me, so that I might proclaim Him among the Gentiles, I did not immediately confer with flesh and blood, nor did I go up to Jerusalem to those who were already apostles before me, but I went away at once into Arabia. And afterwards, I returned to Damascus. Then, after three years, I did go up to Jerusalem to visit Peter, and stayed with him fifteen days. But I did not see any other apostle, except James, the Lord’s brother.
Saint John Chrysostom talks about Saint Paul's defense of himself of having received the Gospel from Jesus,
Observe how sedulously Paul affirms that he was taught of Christ, Who Himself, without human intervention, condescended to reveal to him all knowledge. And if he were asked for his proof that God Himself thus immediately revealed to him these inexpressible mysteries, he would instance his former manner of life, arguing that his conversion would not have been so sudden, had it not been by Divine revelation. For when people have been vehement and eager on the contrary side, their conviction, if it is effected by human means, requires much time and ingenuity.
The Whole Counsel of God Bible study: