William Burkitt on Revelation 18:20

Note here, 1. That as Babylon's ruin was matter of great grief and sorrow to the fore-mentioned mourners who merchandised and traded with her; so it is matter of great joy and rejoicing to all spiritual and heavenly-minded persons, which are the true church, who are commanded to rejoice at it. Rejoice over her, O heaven; that is, ye angels in heaven, or ye saints, that are of an heavenly disposition. And all ye holy apostles and prophets; that is, all faithful ministers who succeed them, who are endued with the same spirit, and teach the same pure and holy doctrine with them.

Note, 2. The cause of this rejoicing declared: For God hath avenged them upon her. The church does not, the saints of God dare not, rejoice at Babylon's calamity as such, but as an act of divine vengeance God will be avenged on Babylon for the doctrine of the gospel corrupted by her, and for the rules of worship violated by her, and for all the barbarities and indignities which his church and people have suffered from her: God will revenge the wrongs of his people, when through want of power they cannot, and through his prohibition they may not, avenge themselves.