Rev 18:2 And he cried mightily with a strong voice, saying, Babylon the great is fallen, is fallen, and is become the habitation of devils, and the hold of every foul spirit, and a cage of every unclean and hateful bird.

Revelation 18 describes the fall of Babylon. Who is this Babylon? Obviously, it’s not the Babylon we read in the book of Daniel. Many think it is Rome. But since when did Rome become unfaithful to God? She has never been a faithful city. Read Revelation 17:5: “MYSTERY, BABYLON THE GREAT, THE MOTHER OF HARLOTS AND ABOMINATIONS OF THE EARTH.” Read the book of Hosea. God’s faithful city, which is Jerusalem, had committed harlotry.

Babylon is Jerusalem! And the context shows that Jerusalem is referred to in this prophecy.
Verse 2: “Babylon the great is fallen.” The Roman Empire did not fall until 400 years later. The war was in Palestine. The fall of Jerusalem is in Christ’s prophecy (Matthew 24). Jerusalem fell in AD70.
Verse 3: “Her fornication.” Rome never committed spiritual fornication. But Jerusalem did.
Verse 4: “…come out of her, my people.” Rome was never God’s people. The Jews were told to flee Jerusalem: “Then let them which be in Judaea flee into the mountains” (Matthew 24:16).
Verse 8: “…she shall be utterly burned with fire.” The only city that was burned to the ground was Jerusalem.
Verse 19: “… and ye holy apostles and prophets; for God hath avenged you on her.” Christ said Jerusalem shed the blood from righteous Abel to Zechariah and it shall be required from that generation (Matthew 23:35, 36).
Verse 21: “Babylon be thrown down, and shall be found no more at all.” Christ said of Jerusalem: “There shall not be left here one stone upon another, that shall not be thrown down” (Matthew 24:2).
Verse 24: “…in her was found the blood of prophets, and of saints.” Jesus said of the Jews: “Ye are the children of them which killed the prophets” (Matthew 23:31).

Note verse 4: “And I heard another voice from heaven, saying, Come out of her, my people, that ye be not partakers of her sins, and that ye receive not of her plagues.”
                                                       
Come out of her, my people – The reasons for this, as immediately stated, are two:
(1)  That they might not participate in her sins; and (2) That they might not be involved in the ruin that would come upon her. It is a warning for us today too. We are commanded to come out from those who work unrighteousness (2 Corinthians 6:17).

Ye be not partakers of her sins - When we have fellowship with liberal and false teachers, we become partakers of their sins. John also wrote concerning fellowshipping those who are false teachers: “For he that biddeth him God speed is partaker of his evil deeds” (2 John 1:11).

That ye receive not of her plagues – Those who preach a different gospel will be condemned in the Day of Judgment (Galatians 1:6-9). Those who follow them will follow them in the destruction.

Time and time again, we have been commanded not to have fellowship with false teachers. We are even told to reprove them (Ephesians 5:11). To reprove is to expose and then to correct. The apostle John writes to admonish these saints to be careful of the association and fellowship given to those who are unwilling to abide in the doctrine of Christ. He further instructs them that if any come to them and refuse to follow the doctrine of Christ, they are not to be received nor welcomed with greetings normally extended to one another (2 John 1:9-11).

Brethren, there is a price to pay for staying with liberal brethren who teach falsely. Are you willing to pay the price? Is it worth? You have been warned: “Come out of her, my people, that ye be not partakers of her sins, and that ye receive not of her plagues.”