Revelation 13:16–18

16 And he causes all, athe small and the great, and the rich and the poor, and the free men and the slaves, 1to be given a bmark on their right hand or on their forehead,

17 and he provides that no one will be able to buy or to sell, except the one who has the amark, either bthe name of the beast or cthe number of his name.

18 aHere is wisdom. Let him who has understanding calculate the number of the beast, for the number is that bof a man; and his number is 1six hundred and sixty-six.