Revelation 13:16-18 NIV

16 He also forced everyone, small and great,1 rich and poor, free and slave, to receive a mark on his right hand or on his forehead,2

References for Revelation 13:16

17 so that no one could buy or sell unless he had the mark,3 which is the name of the beast or the number of his name.4

References for Revelation 13:17

18 This calls for wisdom.5 If anyone has insight, let him calculate the number of the beast, for it is man's number.6 His number is 666.

References for Revelation 13:18