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. Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number [is] Six hundred threescore [and] six (Revelation 13:16-18).
Antichrist will cause all to receive a mark on their right hand or in their forehead through which they can buy or sell, thus establishing a one world economy. He who has understanding will be able to count the number of the first beast which is 666.