John Chrysostom

And that they might not think that they did it all by their own strength, but rather that God permitted it, two things resulted, namely, "Some of them were persuaded," and others did the contrary: the Jews moved with envy. And from the fact that the being called was itself a matter of God's fore-ordering, they neither thought great things of themselves as if the triumph were their own, nor were terrified as being responsible for all.

Homily on Acts 37 ↗

Theophylact of Ohrid

"Of the Greeks that worshipped God a great multitude." By Greeks he means Jews who spoke Greek, or else he means proselytes numbered among the Jews, from among the Greeks. He calls them worshippers of God because they observed the Law.

Commentary on Acts ↗

Oecumenius

He calls them devout [Σεβομένους] Greeks, who, although they were from the Jews, nevertheless spoke Greek: devout because they observed the law; or proselytes of the Jews who were from the Greeks.

Commentary on Acts ↗

Bede

And a great multitude of worshipers and Gentiles; that is, both those who had exchanged their gentile rites for Judaism and those who had remained entirely Gentiles, many joined to Christ.

Commentary on Acts ↗