John Chrysostom

Observe God's providential management. He does not suffer the speech to be finished, nor the baptism to take place upon a command of Peter, but, when He has made it evident how admirable their state of mind is, and a beginning is made of the work of teaching, and they have believed that assuredly baptism is the remission of sins, then forthwith comes the Spirit upon them. Now this is done by God's so disposing it as to provide for Peter a mighty ground of justification. …

Homily on Acts 24 ↗

Theophylact of Ohrid

Notice God's economy. God did not allow Peter's speech to be brought to completion or for baptism to be performed by Peter's order; but as soon as He saw that their minds were filled with amazement and a beginning of instruction had been laid, and they fully believed that baptism is the remission of sins, then the Spirit descended.

Commentary on Acts ↗

Oecumenius

When they had believed that by baptism there is altogether the remission of sins, then the Spirit descended upon them. This, however, happened by God's ordaining for the great defense of Peter. Nor did the Spirit come in a common way, but they also spoke in tongues, which put those who had been companions into astonishment; because of which Peter immediately ordered them to be baptized in the name of the Lord. Nor did he say: Why is water needed, when the Holy Spirit has come upon them? …

Commentary on Acts ↗

Bede

While Peter was still speaking these words, the Holy Spirit fell upon all who heard the word. Then they asked him to stay with them for some days. Lest it be doubted that baptism should be given to the Gentiles, it was confirmed by the testimony of the Holy Spirit, which customarily sanctifies the waters of the font, in a new order of precedence, which it never happened with the Jews, as occurred once for the testimony of the Gentiles' faith.

Commentary on Acts ↗