John Chrysostom
But how, you will say, did unlearned men overcome both them and the high priests in eloquence? It was because they were not the ones speaking, but the grace of the Spirit through them.
Here is another proof, no less than the former. "They recognized them," it says, "that they had been with Jesus." The Evangelist did not place these words without purpose.
He wished to show where they had been with Jesus, namely, at the Passion. Indeed, they alone were then with Christ, and at that time they had been seen as humble and abased.
For this reason the priests were especially amazed at this sudden change. Annas and Caiaphas with their attendants had also been there, and the apostles had stood before them.
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Now they were astonished at their extraordinary boldness. The apostles showed that they cared nothing for being judged over such matters, or for the extreme danger threatening them.
They showed this not only by words, but by appearance, voice, look, and everything else. Before the people they displayed boldness while they spoke.
The priests perhaps marveled because the apostles were unlearned and simple men. A man may be unlearned and yet not simple, or simple and yet not unlearned.
By this the writer shows that both qualities were united in the apostles. "They marveled," it says. At what? At what they said.
Peter speaks few words, but by the very expression and composition of the speech he shows boldness. The priests would have accused the apostles if this man, the lame man, had not been with them.
"They recognized them," it says, "that they had been with Jesus." From this they came to the conviction that they had learned this from Jesus, and that they did everything as His disciples.
The miracle and sign itself uttered a voice no less loud than the apostles' voice. It was precisely this that most of all stopped their mouths.