After Adam's rebellion, God decreed in Genesis 3:15 that from then on there would exist two opposed forms of worship, those who obey Jehovah, and those who follow Satan; and the two would always be at enmity with each other. One cannot worship Jehovah and at the same time have any dealings with Satan and the demons: “The things which the nations sacrifice they sacrifice to demons, and not to God; and I do not want YOU to become sharers with the demons. YOU cannot be drinking the cup of Jehovah and the cup of demons; YOU cannot be partaking of “the table of Jehovah” and the table of demons. –1 Corinthians 10:20,21
That is why the apostle Paul says that there can be no fellowship with unbelievers, just as Christ has nothing to do with the Devil. He addresses all who want to worship Jehovah to "get out from among them, and separate yourselves, and quit touching the unclean thing; and I will take you in. And I shall be a father to you, and you will be sons and daughters to me,’ says Jehovah the Almighty.” (2 Cor. 6:14-18). From this it is clear that those who want to worship Jehovah cannot be sharing in "a system of beliefs and practices" relating to the worship of demons and belong to its "community."
It escapes me as to why many don't make the connection between Revelation 18:4 and the parallel scripture at 2 Corinthians 6:14-18. Jehovah has foretold that he will destroy Satan's entire system of worship referred to in Revelation as "Babylon the Great." It is called Babylon the Great because its worship is rooted and built on the pagan worship of ancient Babylon, from where false religion spread to all corners of the earth. That explains the similarity of many of the world's religious beliefs and customs, including that of the churches of Christendom. Therefore, Babylon the Great includes all the world's religions, including the many churches of Christendom. It does not include God's own people, although they may be just as wicked as the worshipers of other religions around them. That is why God's judgment will start with them, his own house, as we are told: "Now if it starts first with us, what will the end be of those who are not obedient to the good news of God? And if the righteous man is being saved with difficulty, where will the ungodly man and the sinner make a showing?" (1 Peter 4:17-19) After God executes his judgment upon the wicked within his own house, then he will turn his attention on Babylon the Great, the global religious system as described in Revelation chapters 17 and 18. Her destruction will come suddenly, as if in one hour. If we do not want to share in her sins and her fate we must have already removed ourselves from that "system of beliefs" and "community" of adherents. That is very basic and clear enough for us to understand in order to act upon the warning. You might say that Revelation 18:4 is a last call for any who want to worship Jehovah to "get out of her" before it is too late.
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