Revelation 13:16-18

New King James Version

¹⁶ He causes all, both small and great, rich and poor, free and slave, ^(A)to receive a mark on their right hand or on their foreheads, ¹⁷ and that no one may buy or sell except one who has ^[a]the mark or ^(B)the name of the beast, ^(C)or the number of his name.

^18 (D)Here is wisdom. Let him who has ^(E)understanding calculate ^(F)the number of the beast, ^(G)for it is the number of a man: His number is 666.