Revelation 13:16-18

CLV(i) 16 And it is causing all, the small and the great, and the rich and the poor, and the free and the slaves, that they may be giving them an emblem on their right hand, or on their forehead, 17 and that no one may be able to buy or sell except the one having the emblem of the wild beast, or its name, or the number of its name." 18 Here is wisdom. Let him who has a mind calculate the number of the wild beast, for it is the number of mankind, and its number is six hundred sixty-six."