The command to “rejoice” is not limited to “heaven” but is directed also to three groupings of people: the saints, the apostles and the prophets. (In Greek the definite article “the” is attached separately to each group, hence differentiating them as three groups instead of one group of people described with three different terms.) There is no reason to assume that these saints, apostles, and prophets are limited to those who are in heaven as opposed to those yet living on earth. Though the prostitute had targeted the Lamb (Revelation 17:14) and so those who belonged to the Lamb (Revelation 12:17; Revelation 13:7; see further Revelation 2:10, Revelation 2:13), the saints of all ages and places (“my people” of Revelation 18:4) may make a very different sound than the kings, the merchants, and the sailors at Babylon’s fall. Some apostles (e.g., Peter or Paul) had been martyred at the hand of “Babylon” while others may yet be alive (including John himself). Either way they are to rejoice at Babylon’s fall. The same is true of prophets (whether of the old or new dispensation; see 1 Corinthians 12:28; Ephesians 4:11). And all, whether saints or apostles or prophets, will undoubtedly be eager to obey the command to “rejoice!”
20 Rejoice over her, O heaven, and you saints and apostles and prophets, for God has given judgment for you against her!”