Were astonished - They were now convinced that it was Peter, and they were amazed that he had been rescued. As yet they were of course ignorant of the manner in which it was done.

But Peter continued knocking,.... That they might come to him, and let him in; beginning to be impatient, and being very desirous of seeing his friends, as well as being in danger of being taken up, and had to prison again, should any of his enemies come by, who knew him:

and when they had opened the door, and saw him, they were astonished: they could hardly believe their own eyes; it was amazing to them, how it should be, that he should be delivered out of prison, when they knew there was such a strong guard about him.

But Peter continued knocking: and when they had opened the door, and saw him, they were astonished.

12:16 They were astonished. They could hardly believe their own eyes.

16. Peter continued knocking-delay being dangerous.

12:12-19 God's providence leaves room for the use of our prudence, though he has undertaken to perform and perfect what he has begun. These Christians continued in prayer for Peter, for they were truly in earnest. Thus men ought always to pray, and not to faint. As long as we are kept waiting for a mercy, we must continue praying for it. But sometimes that which we most earnestly wish for, we are most backward to believe. The Christian law of self-denial and of suffering for Christ, has not done away the natural law of caring for our own safety by lawful means. In times of public danger, all believers have God for their hiding-place; which is so secret, that the world cannot find them. Also, the instruments of persecution are themselves exposed to danger; the wrath of God hangs over all that engage in this hateful work. And the range of persecutors often vents itself on all in its way.