A.T. Robertson Commentary Acts 8:10

"to whom they all gave heed, from the least to the greatest, saying, This man is that power of God which is called Great." — Acts 8:10 (ASV)

That power of God which is called Great (η Δυναμις του θεου η καλουμενη Μεγαλη). Apparently here already the oriental doctrine of emanations or aeons so rampant in the second century. This "power" was considered a spark of God himself and Jerome (in Mt 24) quotes Simon (Page) as saying: Ego sum sermo Dei,... ego omnipotens, ego omnia Dei. Simon claimed to impersonate God.