In hot countries this was usual, to baptize by dipping the body in the water; and to this the apostle alludes, when he tells the Corinthians, 1 Corinthians 6:1, that they are washed: but God will have mercy, and not sacrifice; sprinkling being as effectual as washing, and as significative also, representing the sprinkling of the blood of the paschal lamb, of which we read, Exodus 12:3, which presignified the sprinkling the blood of Jesus, that Lamb of God which taketh away the sins of the world; and our hearts must by it be sprinkled from an evil conscience, Hebrews 10:22. It is not the more or the less of the outward element which makes the sacraments effectual; but they are effectual only as they are God's appointments, and attended upon according to his will.
Related Commentaries of Acts 8:38
Acts 8:38
38 And he commanded the chariot to stand still: and they went down both into the water, both Philip and the eunuch; and he baptized him.