And there arose on that day a great persecution against the church in Jerusalem, and they were all scattered throughout the regions of Judea and Samaria, except the apostles. 2 Devout men buried Stephen and made great lamentation over him. 3 But Saul was ravaging the church, and entering house after house, he dragged off men and women and committed them to prison. (Acts 8:1-3)
Stephen’s execution was the beginning of severe persecution of the church. And the young man Saul was very active in arresting believers to be punished by the law-courts, even to be sentenced to death.
However there was no further imprisonment of the apostles for a while. They remained in Jerusalem, where previously they had been freed from prison by God (Chapter 6:17-21).