What does Revelation 14:9 mean?

Another angel appears in John's vision and cries out with a loud voice. His message concerns anyone who worships the beast and its image and has the mark of the beast on his forehead or on his hand. This statement makes it clear that anyone who takes this mark is declaring their opposition to God. In simple terms, all who take the mark of the beast are lost—the very act of accepting the beast's image signifies they are unbelievers.

This reference to the worship of the beast and the mark of the beast recalls Revelation 13. In that previous chapter we learn about the rise to political power of the beast from the sea, an apparent reference to the Mediterranean region. This region approximates the territory of the Roman Empire. Apparently, the beast—typically labelled as Antichrist—will rule like a Caesar over the Revived Roman Empire. He guarantees Israel's protection and peace until the middle of the tribulation, when he breaks his treaty with Israel (Daniel 9:27). To gain the first beast's favor, the second beast—the False Prophet—places a statue in Jerusalem in the holy place and commands everyone to worship the beast. He also causes everyone to receive the mark of the beast on his right hand or on his forehead. Failure to comply with the false prophet's order withdraws a person's right to buy and sell.