Revelation 15:5

And after that I looked, and, behold, the temple of the tabernacle of the testimony in heaven was opened:

The opened temple of the tabernacle of the testimony is God's temple in heaven, opened to reveal the ark of His testament. It represents the faithful and obedient. The opening comes after the song of victory over the beast and his image and his mark and his number, and after the revealing of the seven angels having the seven last plagues in whom the wrath of God is filled up. The opened temple is the place from which those seven angels come out with the seven plagues, after which the temple is filled with smoke from the glory and power of God so that no one can enter until the plagues are fulfilled.

The verse marks the time when Jesus finishes His work in the heavenly sanctuary and leaves it, and after He leaves the sanctuary the plagues are poured out. After His work there is finished He comes to the door of the tabernacle, the door of the first apartment, to confess the sins of Israel upon the head of the scapegoat. He then puts on the garments of vengeance and takes His seat upon the great white cloud, which is entirely separate from the holy and the most holy and entirely separate from the sanctuary, and the plagues do not come upon the wicked until He has put on vengeance and taken that seat. While the plagues are falling the scapegoat is being led away into the land of forgetfulness, Jesus has ceased to plead for Israel, and with no man and no intercessor and no mediator between God and man the plagues can be withheld no longer. Those covered with the covering of the Almighty live in His sight, while those not covered feel the plagues because they have nothing to shelter them. The destruction or death of the wicked is caused by the wrath of God and the Lamb.

Chapter 15 belongs with Revelation 14:13-20 and is to be meditated together with the blessing on the dead who die in the Lord, the Son of man on the white cloud with the golden crown and sharp sickle, and the ripe harvest of the earth. The verse belongs to the prophecies of Revelation 12 to 18 that are described as being fulfilled now. Those prophecies form the last message of warning for all to hear, leading to the very last call in chapter 18 and then to the taking of the beast and false prophet, the binding of the dragon for a thousand years, the resurrection of the wicked, the final destruction of Satan and all the wicked, and the final triumph and reign of Christ on this earth. The verse belongs with the first, second, and third angels' messages that are to be proclaimed and explained with zeal and determination under the summons to action and diligent study of the Scriptures.