When Saul arrived in Jerusalem: The believers did not trust him at first. This was understandable. He had recently attacked and imprisoned Christians (8:3; 9:1, 13; 22:3, 4; 26:9–11).
Barnabas helped him. Barnabas, whose name means “Son of Encouragement” (4:36), brought Saul to the apostles. He told them how Saul had seen the Lord on the road to Damascus. He also explained how Saul had preached boldly in the name of Jesus there.
Barnabas convinced the apostles that Saul’s conversion was real. So Saul stayed with them in Jerusalem. There, he continued to preach boldly about the Lord.
Paul later spoke about this visit in Galatians 1:18–19.