Luke
Acts 8:38BSB·traditional attribution

And he gave orders to stop the chariot. Then both Philip and the eunuch went down into the water, and Philip baptized him.

John Calvin Reformed @genevareformer

38. They went down into the water. Here we see the rite used among the men of old time in baptism; for they put all the body into the water. Now the use is this, that the minister doth only sprinkle the body or the head.

Matthew Henry Presbyterian @wholebiblehenry

We have here the story of the conversion of an Ethiopian eunuch to the faith of Christ, by whom, we have reason to think, the knowledge of Christ was sent into that country where he lived, and that scripture fulfilled, Ethiopia shall soon stretch out her hands (one of the first of the nations) unto God, Psa 68:31. I.

Commenting on Acts 8:26-40

John Gill Reformed Baptist @doctorgill

And when they were come up out of the water,.... Which is another circumstance, showing that baptism was then performed by immersion; with this compare Mat 3:16 and so it is said of the high priest, when he washed himself on the day of atonement, , "he went down and dipped, and came up" (m); and so any other person that was obliged to dipping...