Revelation 13:16-17

Amplified Bible

¹⁶ Also he compels all, the small and the great, and the rich and the poor, and the free men and the slaves, to be given a mark on their right hand or on their forehead [signifying allegiance to the beast], ¹⁷ and that no one will be able to buy or sell, except the one who has the mark, either the name of the beast or the number of his name.