Acts 12:1-5

Now about that time Herod the king laid hands on some who belonged to the church, to do them harm.

And he had James the brother of John executed with a sword.

When he saw that it pleased the Jews, he proceeded to arrest Peter as well. (Now these were the days of Unleavened Bread.)

When he had arrested him, he put him in prison, turning him over to four squads of soldiers to guard him, intending only after the Passover to bring him before the people.

So Peter was kept in the prison, but prayer for him was being made to God intensely by the church.