[Rev. 15:1] ¶ Then I saw another great and astounding sign in heaven: seven angels who have seven final plagues (they are final because in them God’s anger is completed). [Rev. 15:2] ¶ Then I saw something like a sea of glass mixed with fire, and those who had conquered the beast and his image and the number of his name. They were standing by the sea of glass, holding harps given to them by God. [Rev. 15:3] They sang the song of Moses the servant of God and the song of the Lamb: “Great and astounding are your deeds, Lord God, the All-powerful! Just and true are your ways, King over the nations![Rev. 15:4] Who will not fear you, O Lord, and glorify your name, because you alone are holy? All nations will come and worship before you for your righteous acts have been revealed.” [Rev. 15:5] ¶ After these things I looked, and the temple (the tent of the testimony) was opened in heaven, [Rev. 15:6] and the seven angels who had the seven plagues came out of the temple, dressed in clean bright linen, wearing wide golden belts around their chests. [Rev. 15:7] Then one of the four living creatures gave the seven angels seven golden bowls filled with the wrath of God who lives forever and ever, [Rev. 15:8] and the temple was filled with smoke from God’s glory and from his power. Thus no one could enter the temple until the seven plagues from the seven angels were completed.
Probably all of John’s original readers had a connection to a believer who died for their testimony of Christ. The tent of heaven is opened up before John and he sees these martyrs. They are not “lost”! They are utterly found! They enjoy a peace beyond comprehension (who can fathom how a sea could be as still as glass?) While they worship (which seems to an involuntary reflex response by those who enter God’s presence) seven plagues are about to be poured out.
The first readers must have been vividly reminded of the last time seven plagues were poured out. It was Egypt. The Hebrews were oppressed. God's wrath against His people’s oppressors was being poured out to bring both vindication and redemption. John deliberately conjures this Biblical imagery to tell his readers something that soon happen. Those already in heaven are already rejoicing. They sing the song of Moses - the song of deliverance from oppression. Soon, these believers would also be rejoicing at their vindication. And the fact that we are discussing these matters at least two millennia later proves that they were.
May we pray that their song will indeed be realized that “all nations will come and worship” God. And may their song be at least partly fulfilled by our willingness to regularly worship together.