John Calvin Commentary Acts 8:9

"But there was a certain man, Simon by name, who beforetime in the city used sorcery, and amazed the people of Samaria, giving out that himself was some great one:" — Acts 8:9 (ASV)

A certain man named Simon. This was such an obstacle that it might seem the gospel could find no way to reach the Samaritans, for all their minds were bewitched by Simon’s deceptions. And this amazement had grown stronger over a long period of time. Furthermore, experience teaches how difficult it is to uproot that error from people's minds which has taken root through long persistence, and to call back to a sound and right mind those who are already hardened. Superstition made them more obstinate in their error, because they regarded Simon not only as a prophet of God, but even as the Spirit of God.