"'Give me this power also, that anyone on whom I lay hands may receive the Holy Spirit.' But Peter said to him, 'Your money perish with you, because you thought that the gift of God could be purchased with money! You have neither part nor portion in this matter, for your heart is not right in the sight of God. Repent therefore of this your wickedness, and pray God if perhaps the thought of your heart may be forgiven you. For I see that you are poisoned by bitterness and bound by iniquity.' Then Simon answered and said, 'Pray to the Lord for me, that none of the things which you have spoken may come upon me.' So when they had testified and preached the word of the Lord, they returned to Jerusalem, preaching the gospel in many villages of the Samaritans" (Acts 8:19-25).
Simon, who was fascinated by the works Philip performed, was very passionate about not only being able to do what Philip did but even to be able to transfer the gifts to others as only the apostles could do! He wanted this ability so badly that he tried to buy it! Out of this transgression, the term "simony" was later coined, where one attempts to buy a religious office. Simon's heart was not right and Peter rebuked him sharply. It was not his place to be an administrator of spiritual gifts. If Simon was allowed to buy such a power, would he not sell it also? It appears this new convert is obsessed with power and is having difficulty breaking free from his old ways! Simon, unless he wanted to perish with his money, was commanded to repent and pray to God if he desired to be forgiven; that is the meaning of Peter's words. Here we learn how a Christian (a baptized, penitent believer) who sins is to seek cleansing: repentance and prayer (cf. I John 1:7-9). There is no need to be immersed again, if one was baptized properly initially. The fact that Simon sinned so quickly after his conversion does not disprove the genuineness of his obedience to the Lord (contrary to the claims of our Calvinistic friends). It does underscore, however, that being baptized into the church is just the beginning of the Christian walk. It typically takes time to fully root out wicked thoughts and evil behaviors (in actuality, such thoughts and behaviors are never far from even the most righteous!). Simon's life has been turned upside down by the gospel and the true power of God and he was still a very weak babe in Christ at this time who would have plunged down the wrong path had the apostles let him. Simon's response to Peter's rebuke is good, and it shows him moving in the right direction (though we have no further information about him beyond this). Although Simon had made a terrible mistake and was struggling to break free from the bonds of materialism, he was not beyond the scope of redemption.
On their way home to Jerusalem, the apostles wisely evangelize along the way throughout the region of Samaria.