John Chrysostom

"Repent ye therefore." "Why? For either it was through ignorance, or by the dispensation of God." "That your sins may be blotted out." I do not mean the crimes committed at the Crucifixion; perhaps they were through ignorance; but so that your other sins may be blotted out: this only. "So shall the times of refreshing come unto you." Here he speaks of the Resurrection, obscurely. For those are indeed times of refreshing, which Paul also looked for, when he said, "We that are in this tabernacle do groan, being burthened."

Homily on Acts 9 ↗

Theophylact of Ohrid

He speaks not of that transgression of the Jews which they dared to commit at the time of the crucifixion, since he said above: "However, I know that you, as well as your rulers, did this in ignorance" (v. 17). What then was the meaning of what he said there, "I know! I know," he says, that is, I consider it beneficial to speak thus, so as to arrange your salvation. And that "you did this in ignorance," I know because many of you are converting and being saved. …

Commentary on Acts ↗

Oecumenius

And by saying, "times of refreshing," he indicates that many hardships are about to happen to them, and that wars will be brought about. For this word would be fitting to one who weeps and longs for relief. "That times of refreshing may come," he says. That is, during the times of refreshment which, from the presence of the Lord, he says will be presided over by the divine and fatherly essence. …

Commentary on Acts ↗