Revelation 13:11-18

Then I saw another beast coming up out of the earth; it had two horns like a lamb, but it spoke like a dragon. It exercises all the authority of the first beast on its behalf and compels the earth and those who live on it to worship the first beast, whose fatal wound was healed. It also performs great signs, even causing fire to come down from heaven to earth in front of people. It deceives those who live on the earth because of the signs that it is permitted to perform in the presence of the beast, telling those who live on the earth to make an image of the beast who was wounded by the sword and yet lived. It was permitted to give breath to the image of the beast, so that the image of the beast could both speak and cause whoever would not worship the image of the beast to be killed. And it makes everyone — small and great, rich and poor, free and slave — to receive a mark on his right hand or on his forehead, so that no one can buy or sell unless he has the mark: the beast’s name or the number of its name. This calls for wisdom: Let the one who has understanding calculate the number of the beast, because it is the number of a person. Its number is 666.