What does Revelation 18:20 mean?This passage has described the fall of a city—possibly representing an entire nation or culture—as judgment from God for their wickedness and evil. Whereas three groups of mourners lament the fall of Babylon, three groups are encouraged to rejoice that Babylon has fallen. Those groups are saints, apostles, and prophets. Interestingly, this declaration comes in the same section as the seafarers' mourning, suggesting they are the ones telling the saints to rejoice. Ancient writings were not composed with paragraphs as is modern text. The statement of rejoicing might be an aside, not necessarily something the world's sailors themselves said. That being the case, the seafarers might well recognize that what is happening to Babylon is divine judgment and react accordingly.
Heaven rejoices over one sinner that repents (Luke 15:7), and it rejoices when Babylon collapses. God and God alone is in the business of securing vengeance for his people (Romans 12:19). His vengeance may not come immediately, or as soon as we would prefer (Habakkuk 1:2; Revelation 6:10). But when it does, it comes with full recompense. He does not let wrong triumph over right (Psalm 37:28). The beast's end-times reign (Revelation 13:1–10) is characterized by ego, greed, cruelty, and injustice, but with one powerful stroke God puts an end to it. God's judgment vindicates His righteous, holy character.
As used in the Bible, "saints" are believers: saved Christians whom God has set apart to Himself. "Saints" is not a term for specially-holy persons; it means anyone who has believed in Christ (John 3:16). "Apostles" are those who saw the risen Lord and received a commission from Him to preach the gospel (Acts 1:2). "Prophets" were those gifted by the Lord to disclose His will to the church before the New Testament was complete. They were also foretellers of the Word.
It seems all three groups view Babylon's judgment from heaven. Babylon's judgment was recompense for what the saints, apostles, and prophets had suffered.