When John claims that I saw in heaven another great and marvelous sign, he recalls for us the "great and wondrous sign" in heaven in 12:1 ("a woman clothed with the sun") and "another sign . . . in heaven" in 12:3 ("an enormous red dragon"). The third sign, so long in coming, consists of seven angels with the seven last plagues--last, because with them God's wrath is completed (v. 1). The terrible harvest of chapter 14 is not quite the end; there is one more series to come.
The seven angels are introduced ceremoniously, as were the angels who began blowing the seven trumpets in chapter 8. In that chapter John saw first the seven angels with their trumpets (8:2). Then "another angel" came and presented "the prayers of all the saints" like incense at the altar in heaven, filled the censer with fire from the altar and poured the fire on the earth in judgment (8:3-5). Finally the seven angels went into action, blowing their trumpets one by one (8:6--11:19). The pattern here is similar. John sees first the seven angels (15:1). Then instead of the saints' prayers entering heaven, the saints themselves appear (vv. 2-4). Finally the seven angels go into action (vv. 5-8) with seven golden bowls filled with the wrath of God (v. 7), which are then poured out on the earth one at a time (16:1-21).
Why is the judgment triggered by "the prayers of the saints" in the first instance and by the presence of the saints themselves in the second? The common theme is sacrifice. Prayers are regarded as sacrifice represented by incense (8:3-5). The deates of the martyrs have also been pictured as sacrificial in nature (14:1-5). Here too the redeemed have come through the blood and the fire of martyrdom. They stand at the sea of glass in heaven (compare 4:6), its shining surface reflecting the fire and torches surrounding it (compare 4:5), as well as the fire of persecution out of which the martyrs have come. They are specifically identified as those victorious over the beast and his image and over the number of his name (v. 2). Evidently they are the same group as the 144,000 in the preceding chapter, except they are no longer on "Mount Zion" but in heaven, with harps given them by God (v. 2), corresponding to the harps from heaven that played the "new song" that only the 144,000 were able to learn (14:2-3). Having learned the song, they are now ready to sing it. This image of the redeemed playing harps is probably the source of many modern depictions, in cartoons and in the public imagination, of humans becoming angels and playing harps all day long as their principal occupation in heaven.
The image in its context has a very serious purpose. John identifies the new song as the song of Moses the servant of God and the song of the Lamb (v. 3). Quite clearly, it is not a song about Moses or about the Lamb, but the song of both jointly about the Lord God Almighty, celebrating the power and justice of the God of Israel and "King of the nations" (v. 3 NRSV) and introducing the last series of God's righteous judgments. Like the "eternal gospel" proclaimed from heaven (14:6), the song is not distinctively Christian. It encompasses the worship of Jew and Christian, Hebrew and Greek, Moses and the Lamb alike. Indeed it sounds like a postscript to the "eternal gospel," asking, Who will not fear you, O Lord, and bring glory to your name? For you alone are holy (v. 4). The song is Jewish to the core, yet comes to a focus in the expectation of Jew and Christian alike that all nations will come and worship before you, for your righteous acts have been revealed (v. 4).
The song (vv. 3-4) serves to place the judgments to follow in the setting of God's holiness and justice. When it is finished (v. 5), John sees the temple, or sanctuary in heaven, opened for the second time in his visions (compare 11:19). It is not like the magnificent Jerusalem temple destroyed by the Romans in A.D. 70, or even the temple first built by Solomon. John defines it rather as the tabernacle of the Testimony, corresponding to the tent where Moses and the people of Israel experienced the glory of the Lord in the desert after the Exodus (Ex 38:21; 40:34; compare Acts 7:44). It was called the tent of "testimony," or "covenant," because it contained the ark of the covenant. Even though the ark is not mentioned here, what John sees recalls his earlier vision of the ark in the sanctuary (11:19). Thus the seven bowls begin precisely where the seven trumpets ended.
As the seven angels receive seven golden bowls filled with the wrath of God from one of the four living creatures (v. 7), John sees the sanctuary filled with smoke from the glory of God and from his power, so that no one could enter the temple until the seven plagues of the seven angels were completed (v. 8). This description evokes the scene in the desert after the Exodus, when "Moses could not enter the Tent of Meeting because the cloud had settled upon it, and the glory of the LORD filled the tabernacle" (Ex 40:35). The seven plagues to follow (16:1-21) will reenact several of the Exodus plagues on Egypt, but because these are the last plagues (v. 1), the order of the Exodus events is reversed. John sees the glory of God in the tabernacle of the Testimony first, and after that the plagues, sent not to free God's people from slavery (the redeemed are already free), but as a last effort to bring the earth's inhabitants, like Pharaoh, to repentance.