"And he causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads: And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name."
Buying and selling is Bible lingo for the sending forth of the gospel: "Ho, every one that thirsteth, come ye to the waters, and he that hath no money; come ye, buy, and eat; yea, come, buy wine and milk without money and withoutprice." When someone receives the gospel they are bought by what the Lord paid on the cross. When they are unsaved they have been sold into the slavery of sin: "Lest there be any fornicator, or profane person, as Esau, who for one morsel of meat sold his birthright."
Rev 13 is talking about a time when the congregations of the church age are overrun by the spirit of error, when those in the congregations are not allowed to preach without having been marked by the wrong spirit. The true believers who have the true gospel are all rejected in that arena. Just as 'buying and selling' is Bible lingo (parable language) for something different than literal buying and selling in a store, so the idea of a mark is not meaning a literal mark. True believers are said to have been sealed in their foreheads, meaning that they have been given the mind of Christ, his spirit, not a physical literal mark on the forehead. Similarly, those in the false congregations have the spirit of their master, not a literal physical mark.
