The disciples underwent three years of training with Jesus. He taught them the ways of God in an unencumbered way, cleaning up the law to reveal the truth, and began training His disciples in that truth. Later on, after the death and resurrection of Jesus, Paul comes along, knows the Law of Moses, and becomes a Christ follower. The Jews hated him more than any of the others because of his incredible conversion, and because he was much more zealous and successful at bringing the gospel, so they came after him more fiercely. He left for Arabia because they were after him. His brilliance did not eliminate him from needing training, and as soon as he could, he came back to Damascus and spent three years there. Here’s the thing, you have to train to become proficient in God’s word. My own Bible training was for three years, but I continue to dig in and learn as much as I can about the ways of Jesus. This is why it’s important that you are involved in Bible study through your church. You must know the Word in order to teach it.
And he spoke and disputed against the Hellenists. But they were seeking to kill him. And when the brothers learned this, they brought him down to Caesarea and sent him off to Tarsus. Acts 9:29-30
nor did I go up to Jerusalem to those who were apostles before me, but I went away into Arabia, and returned again to Damascus. Then after three years I went up to Jerusalem to visit Cephas and remained with him fifteen days. Galatians 1:17-18