Albert Barnes Commentary Acts 8:13

"And Simon also himself believed: and being baptized, he continued with Philip; and beholding signs and great miracles wrought, he was amazed." — Acts 8:13 (ASV)

Then Simon himself believed also. That is, he believed that Jesus had performed miracles and was raised from the dead, and so on. All this he could believe, in entire consistency with his own notions of the power of magic. And all that the connection requires us to suppose is that he believed this—that Jesus had the power of working miracles, and so on; and as he intended to turn this to his own account, he was willing to profess to be his follower.

Moreover, it might have injured his popularity if he had taken a stand when so many were professing to become Christians. Men often profess religion because, if they do not, they fear they will lose their influence and be left with the ungodly. That Simon was not a real Christian is apparent from the whole narrative (Acts 8:18, 21-23).

And when he was baptized. He was admitted to a profession of religion in the same way as the others. Philip did not pretend to know the heart; and Simon was admitted because he professed his belief. This is all the evidence that ministers can have, and it is no wonder that they, as well as Philip, are often deceived. The reasons which influenced Simon to make a profession of religion seem to have been these:

1. An impression that Christianity was true. He seems to have been convinced of this by the miracles of Philip.
2. The fact that many others were becoming Christians; and he went in with the multitude. This is often the case in revivals of religion.
3. He had no religion; but it is clear from Acts 8:20, 21 that he was willing to make use of Christianity to advance his own power, influence, and popularity—a thing which multitudes of men of the same mind as Simon Magus have since been willing to do.

He continued, etc. It was customary and natural for the disciples to remain with their teachers. See Acts 2:42.

And wondered. This is the same word that is translated bewitched in Acts 8:9, 11. It means that he was amazed that Philip could really perform so much greater miracles than he had even pretended to. Hypocrites will sometimes be greatly attentive to the external duties of religion and will be greatly surprised at what is done by God for the salvation of sinners.

Miracles and signs. Greek, Signs and great powers, or great miracles. That is, so much greater than he pretended to be able to perform.