John Calvin Commentary Acts 8:38

"And he commanded the chariot to stand still: and they both went down into the water, both Philip and the eunuch, and he baptized him." — Acts 8:38 (ASV)

They went down into the water. Here we see the rite used among people in ancient times for baptism, as they immersed the whole body in the water. Now the practice is that the minister only sprinkles the body or the head. But we should not be so concerned about such a small difference in a ceremony that we would therefore divide the Church or trouble it with disputes.

We should rather fight even a hundred times to the death for the ceremony of baptism itself, since it was delivered to us by Christ, than allow it to be taken from us.

But since we have a testimony of our washing as well as of newness of life in the figure of water; since Christ represents His blood to us in the water as in a mirror, that we may obtain our cleanness from it; since He teaches that we are made anew by His Spirit, so that, being dead to sin, we may live to righteousness—it is certain that we lack nothing that pertains to the substance of baptism.

Therefore, the Church, from the beginning, granted herself the liberty to change the rites somewhat, apart from this substance.

For some dipped them three times, and some only once.

Therefore, there is no reason why we should be so rigid in matters that are not of such great importance, provided that external pomp does not in any way corrupt the simple institution of Christ.