Albert Barnes Commentary Acts 12:10

"And when they were past the first and the second guard, they came unto the iron gate that leadeth into the city; which opened to them of its own accord: and they went out, and passed on through one street; and straightway the angel departed from him." — Acts 12:10 (ASV)

The first and the second ward. The word which is here rendered ward, fulakhn, properly denotes the act of guarding, but it is most commonly used to denote a prison or place of confinement. In this place, it seems to denote the guard itself—the soldiers stationed at intervals in the entrance to the prison. These were passed silently, probably because a deep sleep had been sent upon them to facilitate Peter's escape.

The iron gate. The outer gate, secured with iron, as the doors of prisons are now.

That leadeth unto the city. Or, rather, into eiv the city. Jerusalem was surrounded by three walls. (See Lightfoot on this place.) The prison is supposed to have been situated between two of these walls. And it is probable that the entrance to the prison was immediately from the inner wall, so that this gate opened directly into the city.

Of his own accord. By itself. It opened spontaneously, without the application of any force or key, thus showing conclusively that Peter was delivered by miraculous interposition.

And passed on through one street. Until Peter was entirely safe from any danger of pursuit, and then the angel left him. God had effected his complete rescue, and now left him to his own efforts, as usual.