Simon . offered them money. From hence it is called the sin of simony, to buy, sell, or give money for benefices, and spiritual things. It was vanity that made Simon desire this power. (Witham)
Hence to give or receive money in exchange, or as a price for any spiritual good whatever, is justly esteemed sinful. It is called simony, from the name of the person, who was first engaged in this sin. (Haydock)
Simon acts the part of a tempter to the apostles, and wishes to draw them into prevarication, by offering money for what was above all price, and of what they were not the proprietors, but the dispensers. (St. Clement of Rome)
He offered them money. (v. 18, 19.) What? Had he seen the others doing this? Had he seen Philip? Did he imagine they did not know with what mind he came to them?