Acts 8:20

But Peter said to him
With great abhorrence and indignation, resenting and detesting his proposal:

thy money perish with thee;
or "go into destruction with thee"; signifying, that he would not touch his money, or have anything to do with that or him either, in any such way: the words do not so much design an imprecation on his person, as an abhorrence of his sin; and rather show what his sin deserved than what he desired might be; for the apostle did not simply wish his damnation, since he afterwards exhorts him to repentance, and to pray for forgiveness; but threatens, and even predicts what would be his case, should he live and die in such a state, in which he appeared to be:

because thou hast thought that the gift of God;
the Holy Ghost, and his extraordinary gifts, which are freely given, when and to whom the Lord himself pleases:

may be purchased with money;
he appears to have a wrong notion of the Spirit of God and his gifts, and of the grace of in bestowing them; as well as a wicked design of purchasing them with money, in order to sell them again; so that it was a sullying and lessening of the grace of God, as well as seeking himself, his own ambition, and filthy lucre: and let such observe how near they come to his sin, who seek to obtain the grace of justification, and the free gift of eternal life, by their own works.