Under the Roman Empire, citizens gave their allegiance to the emperor Caesar by worshipping him, by declaring publicly that Caesar is lord & by placing a pinch of incense on his altars. "The burning of the pinch of incense was rewarded by a certificate which had to be renewed annually. Failure to produce a certificate meant being branded as a Christian." Please read the 3 following articles for more information at
Likewise the mark of the beast 666 in the forehead or in the right hand will symbolize allegiance to the beast & and that the bearer worships the beast, his image & Satan. (Rev. 13:4, 8, 15; Rev. 14:9, 11.) The mark will also allow them to buy and sell. Also it will be easier to pinpoint, single out & track down those that don't have the mark yet upon their forehead or in their right hand so that they too can be given the opportunity to worship him and his image and then to receive his mark. Anyone not worshipping the beast and his image will be killed ( beheaded), and will not receive his mark in the forehead nor in the right hand. Just like the pinch of incense on the Roman Emperor's altar and declaring that the Emperor (Caesar) is lord was rewarded with an annual certificate, the reward for taking the mark of the beast (Antichrist) will enable one to buy and sell.