12 So, when he had considered this, he came to the house of Mary, the mother of John whose surname was Mark, where many were gathered together praying. 13 And as Peter knocked at the door of the gate, a girl named Rhoda came to answer. 14 When she recognized Peter's voice, because of her gladness she did not open the gate, but ran in and announced that Peter stood before the gate. 15 But they said to her, "You are beside yourself!" Yet she kept insisting that it was so. So they said, "It is his angel." 16 Now Peter continued knocking; and when they opened the door and saw him, they were astonished.
Matthew Henry's Commentary on Acts 12:12-16
Commentary on Acts 12:12-19
(Read Acts 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.