John Calvin Commentary Acts 8:15

"who, when they were come down, prayed for them, that they might receive the Holy Spirit:" — Acts 8:15 (ASV)

They prayed. Undoubtedly they taught first, for we know that they were not mute; but Luke passes over what was common to them and Philip, and declares only what new thing the Samaritans had by their coming, namely, that the Spirit was given to them then.