Acts 12:13

And as Peter knocked at the door of the gate, a damsel came to hearken, named Rhoda.

This knock at the outer gate belongs to the account of Peter's imprisonment and miraculous release, placing his deliverance in an ordinary household setting as he seeks entry after escaping prison. The deliverance took place under Herod Agrippa, tetrarch of Galilee ruling Judea under the Roman emperor Claudius, a professed proselyte to the Jewish faith who was zealous for the ceremonies of the law and sought Jewish favor to secure his offices and honors. He persecuted the church of Christ, spoiled the houses and goods of believers and imprisoned its leading members, and he killed James the brother of John with the sword by beheading, as an earlier Herod had beheaded John, and then imprisoned Peter also when he saw that this pleased the Jews.

Herod intended to put Peter to death, but God had work for him to do and sent an angel to deliver him. In answer to prayers made on his behalf, God sent His angel to deliver Peter from prison, loosing his bands and opening the prison doors at the angel's presence. Awakened by the angel's touch amid light, Peter thought he saw a vision and was amazed until he was set free.

At once after his deliverance, Peter went to the house where his brethren were assembled in prayer for him and knocked at the door of the gate. The prayers then being offered for him were earnest. A servant girl named Rhoda came to listen and answer at the gate and recognized Peter's voice. Her joy and gladness at recognizing him made her run inside to tell the others without opening the gate instead of opening it.

The believers did not believe her report at first and initially doubted it. Peter kept knocking until they let him in and heard how the Lord had rescued him from prison. His arrival alive at the gate was the direct answer to the prayers then being offered for him, showing that God had heard and answered their prayers and delivered Peter from prison and from the hands of Herod. His arrival began the believers' astonished recognition that God had delivered Peter and filled them with joy and praise.

Those praying heard his voice at the gate with astonishment because they expected he would have to suffer death like James, who had been beheaded after the king saw it pleased the Jews. This proves that God has care for the true and faithful and sends messengers from heaven to open gates and set His servants free.