Revelation 13:16-18

Complete Jewish Bible

¹⁶ Also it forces everyone — great and small, rich and poor, free and slave — to receive a mark on his right hand or on his forehead ¹⁷ preventing anyone from buying or selling unless he has the mark, that is, the name of the beast or the number of its name. ¹⁸ This is where wisdom is needed; those who understand should count the number of the beast, for it is the number of a person, and its number is 666.