John Chrysostom
Behold yet another gain, another teaching expressed in the form of a defense. “We are His witnesses in these things.” What great boldness!
Then, for greater trustworthiness of his words, Peter added: “and so is the Holy Spirit, whom God has given to those who obey Him.”
Do you see how the apostles present not themselves alone as witnesses, but also the Spirit? They did not say, “He gave Him to us,” but “to those who obey.”
Thus they show their own humility, the greatness of the Spirit, and also that the Jews too can receive Him.
Notice how they were instructed both by deeds and by words, yet did not heed. For this reason righteous condemnation will overtake them.
Read more (81 words)
God allowed the apostles to be led to trial so that the others might be edified, if they wished to learn, and so that the apostles might show boldness.
Boldness about what? That Christ proclaimed remission and repentance, since His Resurrection had already been acknowledged as beyond doubt.
And that He grants remission, to this we and the Holy Spirit are witnesses. The Spirit would not have come down unless sins had first been remitted. Thus this is an undoubted sign.