Revelation 13:14-18

And he deceiveth them that dwell on the earth by reason of the signs which it was given him to do in the sight of the beast; saying to them that dwell on the earth, that they should make an image to the beast who hath the stroke of the sword and lived. And it was given unto him to give breath to it, even to the image of the beast, that the image of the beast should both speak, and cause that as many as should not worship the image of the beast should be killed. And he causeth all, the small and the great, and the rich and the poor, and the free and the bond, that there be given them a mark on their right hand, or upon their forehead; and that no man should be able to buy or to sell, save he that hath the mark, even the name of the beast or the number of his name. Here is wisdom. He that hath understanding, let him count the number of the beast; for it is the number of a man: and his number is Six hundred and sixty and six.