John Chrysostom

And when they were come up out of the water, the Spirit of the Lord caught away Philip, that the eunuch saw him no more: and he went on his way rejoicing. But why did the Spirit of the Lord bear him away? Hereby the occurrence was shown to be more wonderful. Even then, the eunuch did not know him. Consequently this was done, that Philip might afterwards be a subject of wonder to him. For, it says, he went on his way rejoicing.

Homily on Acts 19 ↗

Theophylact of Ohrid

"An Angel of the Lord caught Philip away." An Angel takes him, thereby adding greater wonderousness to what had happened, and at the same time bringing joy to Philip as well, that he was deemed worthy of the same things as the prophets, such as Habakkuk. It was good that he was taken from the eunuch, because the eunuch would have asked Philip to go with him, and Philip would have grieved him if he had refused due to the demands of circumstances.

Commentary on Acts ↗

Oecumenius

The Spirit seized Philip, for though the eunuch had indeed wished to converse, Philip, refusing and denying because it was not yet time, nevertheless would have grieved him. Philip himself also gained very much profit, seeing that what he had heard in Ezekiel and Habakkuk was fulfilled in him. [CHRYSOSTOM]

Commentary on Acts ↗

Bede

The Spirit of the Lord snatched Philip away. There are some who testify that an angel did this in the Holy Spirit, as Jerome reports.

Commentary on Acts ↗