John Chrysostom

And as they went on their way, they came unto a certain water: and the eunuch said, See, here is water; what doth hinder me to be baptized? Mark the eager desire, mark the exact knowledge. Then, it says, they came to a certain water, and he said, Lo, here is water. Again, of his own accord he requests, saying, What doth hinder me to be baptized? And see again his modesty: he does not say, Baptize me, neither does he hold his peace; but he utters somewhat midway betwixt strong desire and reverent fear, saying, What doth hinder me?

Homily on Acts 19 ↗

Theophylact of Ohrid

"Behold, water; what hinders me from being baptized?" See how prudently he acts. First he reads and does not understand, then he reads the same prophecy; it contains the teaching about the suffering, the resurrection of Jesus Christ, and the bestowal of the grace of the Holy Spirit. Then he asks to be baptized; Philip explains to him in order, beginning from this prophecy. And having been uplifted by his readiness, he is gradually led to baptism. …

Commentary on Acts ↗

Oecumenius

It should be observed that great zeal existed among Christians entirely for the sensible baptism. Since what is given is twofold, sometimes through water, sometimes in the Holy Spirit and fire, they did not despise the more bodily one on account of the superiority of the baptism in the Spirit. For this also contributes to salvation and to the resurrection of the body. [DIDYMUS]

Commentary on Acts ↗

Bede

Who prohibits me from being baptized? And he commanded the chariot to stop, and the rest. Here another translation according to the Greek exemplar has a few more verses where it is written: Behold water, who prohibits me from being baptized? But Philip said to him: If you believe with all your heart, you will be saved. And responding, he said: I believe in Christ, the Son of God. And he commanded the chariot to stop, and the rest. …

Commentary on Acts ↗