A.T. Robertson Commentary Revelation 18:20

"Rejoice over her, thou heaven, and ye saints, and ye apostles, and ye prophets; for God hath judged your judgment on her." — Revelation 18:20 (ASV)

Rejoice over her (Ευφραινου επ' αυτη). Present middle imperative of ευφραινω, for which verb see 11:10, used there of the joy of the wicked over the death of the two witnesses, just the opposite picture to this. "The song of doom" (Charles) here seems to be voiced by John himself.

God hath judged your judgment (εκρινεν ο θεος το κριμα). First aorist (prophetic) active of κρινω and cognate accusative κριμα, here a case for trial (Exodus 18:22; 1 Corinthians 6:7), not a sentence as in 17:1. God has approved the case of heaven.