John Calvin on Acts 4:4

4. And many of them which heard The apostles are put in prison, but the force of their preaching is spread far and wide, and the course thereof is at liberty. Of which thing Paul boasteth very much, that the Word of God is not bound with him, (2 Timothy 2:9.) And here we see that Satan and the wicked have liberty granted them to rage against the children of God; yet can they not (maugre their heads “Omnia machinando,” by all their machinations. ) prevail, but that God doth further and promote the kingdom of his Son; Christ doth gather together his sheep; and that a few men unarmed, furnished with no garrisons, do show forth more power in their voice alone, than all the world, by raging against them. This is, indeed, no common work of God, that one sermon brought forth such plentiful fruit; but this is the more to be wondered at, that the faithful are not terrified with the present danger, and discouraged from taking up the cross of Christ together with the faith. For this was a hard beginning for novices. Christ did more evidently declare by this efficacy and force of doctrine that he was alive, than if he should have offered his body to be handled with hand, and to be seen with the eyes. And whereas it is said that the number of those which believed did grow to be about five thousand, I do not understand it of those which were newly added, but of the whole church.

Acts 4: 5-12

5. And it came to pass, that the next day their rulers, and elders, and scribes, were gathered together at Jerusalem. 6. And Annas the high priest, and Caiaphas, and John, and Alexander, and so many as were of the kindred of the priests, 7. And when they had set them before them, they asked them, In what power, or in what name, have ye done that? 8. Then Peter, being filled with the Holy Ghost, said unto them, Ye rulers of the people, and elders of Israel, 9. If we be judged this day for healing the man which was lame, by what means he is made whole: 10. Be it known unto you all, and to all the people of Israel, that in the name of Jesus Christ of. Nazareth, whom ye have crucified, whom God hath raised up from the dead, this man standeth before you whole. 11. This is the stone which was refused of you the builders; it is placed in the head of the corner. 12. Neither is there salvation in any other. Neither is there any other name given under heaven unto men, wherein we must be saved.