Revelation 13:16-18

New International Version

¹⁶ It also forced all people, great and small,^(A) rich and poor, free and slave, to receive a mark on their right hands or on their foreheads,^{(B) 17} so that they could not buy or sell unless they had the mark,^(C) which is the name of the beast or the number of its name.^(D)

¹⁸ This calls for wisdom.^(E) Let the person who has insight calculate the number of the beast, for it is the number of a man.^[a](F) That number is 666.