John Chrysostom

"Then certain of the vagabond Jews, exorcists, took upon them to call over them which had evil spirits the name of the Lord Jesus, saying, We adjure you by Jesus whom Paul preacheth." So entirely did they do all by way of trade! Observe: vagabond, or, itinerant, Jewish exorcists. And to believe indeed, they had no mind; but by that Name they wished to cast out the demons. "By Jesus, whom Paul preacheth." Only see what a name Paul had got! Wonderful, how great the power of them that have believed! …

Homily on Acts 41 ↗

Theophylact of Ohrid

They did not wish to believe, yet desired to cast out demons in the name of Jesus, because these words clearly reveal that these exorcists adjured the unclean spirits in the name of our Lord Jesus Christ not as those who believed in Jesus, but as those who were testing Him. And the expression "began to use" shows that, although they did not hope for success, they nevertheless laid on hands in order to achieve the purpose of their test. Therefore, shortly after, they paid the penalty for their recklessness.

Commentary on Acts ↗

Oecumenius

"Some of the roaming Jewish exorcists." This statement shows that they did not, like exorcists believing in Jesus, adjure unclean spirits in the name of the Lord, but were testing them: wherefore also, since they were not faithful, as the evil spirit says, they shortly paid the penalty of their foolishness. For the spirit exposed them, and wholly exposed their deceit, moved by anger: as when one placed in extreme dangers is attacked by some enemy, and all wrath is poured out upon him.

Commentary on Acts ↗

Bede

However, certain itinerant Jewish exorcists attempted to invoke over those who, etc. Josephus reports that King Solomon devised and taught his people modes of exorcism, that is, adjurations, by which unclean spirits, once expelled from a person, might not dare to return. …

Commentary on Acts ↗