Johns vision at the beginning of Chapter 15 opens with seven angels arrayed before him, each holding a πληγή | plēgē, translated as a “blow” or a “stroke,” such as the blow of an axe or the strike of lightning. Plēgē can also be translated as “plague” or “calamity.” Perhaps all these meanings were in John’s mind as his eyes widened at the scene.
After John took in the angels, he saw the glassy sea spread out beneath or before them, and a scene of worship and adulation. This time, the sea seemed to be mixed with fire, and the song ringing throughout heaven came from the lips of those who had persevered victoriously through all the beasts’ persecution.
Historicists and preterists see this scene as having been fulfilled.
But futurists are still waiting.

Futurist
The seven angels will each soon be given a bowl filled with God’s wrath. They appear now in preparation for this final assignment, to pour out God’s remaining judgment upon the earth.
When John saw the glassy sea, it became apparent this was not simply an apparition in the sky, but rather a scene in heaven, in God’s throne room. Before, the sea was described as luminescent, as clear as a crystal, reflecting the brilliance emanating from the Lord. But now, the sea flickered with the fury of God.
Not the Rapture
Those standing upon the glittering sea cannot be all those who had already met Jesus in the clouds in the Rapture. The Church has already been drawn up into heaven to fulfill God’s promise of protection.
So, these triumphant believers must be those who came to saving faith in Jesus during the seven years of the Great Tribulation. They are now in heaven because
- their bodies were put to death by the dragon and its dangerous creatures for defying the Mark of the Beast, and worship of the beast, and their disembodied spirits are in heaven,
- or no sooner were they martyred, God raptured them bodily up into heaven.
Either way, it is pointed out that God’s wrath will not be poured out until every believer has been taken up to God. They had endured the wrath of the dragon, and they had endured the persecution of its creatures, but they would be spared these final seven bowls of God’s judgment.
On the earthly plain, it will seem as though the dragon is getting the victory over God, and God’s people. Christians will dwindle in number until there are no more, as the dragon rampages through the nations, and the beasts do its bidding. No mercy will be shown to those who resist their agenda.
But in reality, it is God who is victorious, and God’s people triumphant, as John saw and heard, for he called them “the ones prevailing from out of the dangerous beast and from out of the image of it and from out of the number of its name” (Revelation 15:2).
This is so often how it is today. From the earthly perspective, it seems as though all is lost, God’s way is waning, Christians are weakening, Christianity itself is being overcome. But the heavenly perspective says otherwise.
So, Who Are They?
Who exactly these people are is under debate.
Perhaps they are the martyrs playing harps in Chapter 14,
Then I heard a sound from the sky as a sound of many waters, and as a sound of mighty thunder, and the sound that I heard as a harpist strumming with their lyres.
And they are singing as it were a new song in the presence of the throne
Revelation 14:2-3
Perhaps they are the two witnesses who were raised back up from the dead in Chapter 11,
Then, after the three and a half days, a spirit of life from God entered into them, and they stood upon their feet, and great fear fell upon those watching them.
And they heard a great voice from the sky saying to them, “You ascend here,” and they ascended into the sky in the cloud, and their enemies looked on.
Revelation 11:11-12
Perhaps they are the great multitude John observed in Chapter 7,
After these things I saw, and behold a vast multitude which no one was able to number, out of every nation and tribes and peoples and languages, who were standing before the throne and before the Lamb, having been arrayed with white robes and palm branches in their hands.
Revelation 7:9

Frescos in the Baptistry (Padua) (Apocalypse) | By Giusto de Menabuoi – Public Domain
The Song of Moses, the Song of the Lamb
These must be two songs.
The first song was a rousing anthem of uproarious thanksgiving that Moses and Miriam led the Hebrew people in singing on the shores of the Red Sea. Because many of Jewish faith and heritage will turn to Jesus during the Great Tribulation, it makes sense they would reach into their scriptures and recognize this as their Second Exodus.
The second song also has echoes in the Exodus, for it sings of the redemption bought by the blood of the lamb painted on the doorframes of all those who heeded Moses’s instructions. Now, the blood of Jesus, Lamb of God, is metaphorically painted on the lintels of every believer’s heart.
Both are songs of rescue and redemption, of dying to the old life and being born into the new. The water speaks both of the release of God’s people from their captors, literal salvation, and also a baptism into their new life as the nation of Israel, the people of God. The blood speaks both of a death and salvation from death, for the lamb died in the place of the people in the house.
Still, futurists see the Song of Moses representing earthly deliverance, and the Song of the Lamb representing spiritual deliverance.
Every Nation
The most remarkable prophecy yet to be fulfilled comes at the end of this oracle:
Every people group will have come and will lie prostrate in homage in Your presence, because Your righteous acts and judgments are made manifest.
Revelation 15:4
Spiritual

The seven angels either represent the last era of earthly history, the Final Judgment of all humanity, or the final judgment of individuals who have persistently, consistently resisted God’s invitation of redemption. John’s portrayals, then, are to be seen as the life course of each person who has lived, throughout history. From this point of view, there comes a time in every human being’s life when a series of choices comes to a final choice from which there is no turning back. Scripture seems to speak of this in such passages as
So teach us to count our days
Psalm 90:12 (NRSVUE)
that we may gain a wise heart.
And
I mean, brothers and sisters, the appointed time has grown short
1 Corinthians 7:29 (NRSVUE)
And
Yet you do not even know what tomorrow will bring. What is your life? For you are a mist that appears for a little while and then vanishes.
James 4:14 (NRSVUE)
The transparent sea of glass reveals God’s righteousness rather than a sense of God’s wrath in judgment. God’s righteousness brings justice, and in that sense God’s wrath is not about rage and fury, but rather about cleansing and purifying, so that what remains is good and right.
The Song of Moses and the Song of the Lamb are but two names for one song about deliverance, for God’s great act of salvation at the Red Sea foreshadowed God’s far mightier act of salvation at the cross of Christ.
Moses, Miriam, and Aaron led the first Exodus of the Hebrews out of captivity and enslavement in Egypt into freedom in the Promised Land. Jesus leads the second Exodus of all people of faith out of captivity and enslavement to sin into freedom in the promised new heavens and earth.
This song, sung by those triumphant in faith, prophesies of a time when not one nation – the nation of Israel – will belong to God, worship God, and be God’s people, but all nations will fall prostrate before God.
Every knee will be bent in humility, every tongue will testify to this truth: Your righteous acts and judgments are made manifest (Revelation 15:4).

More details
Rose window of Sainte-Chapelle (Paris) | By Maître d’Anne de Bretagne – [1], Public Domain
The four perspectives taken from Revelation: Four Views A Parallel Commentary, edited by Steve Gregg