Most commentaries I have reviewed on this subject describe the Sea of Glass in Revelation 4:6 and 15:2 in rather vague fashion, as using symbolic terms of splendor that somehow are meant to portray heavenly mysteries.
There’s a bit more precision to it than that. I believe scripture’s intentions are to give us a view of a kind of Temple dedication ceremony in heaven, with purification rites for the resurrected saints just before these victorious saints who had remained faithful until death were allowed to enter heaven’s Temple at their bodily resurrection in AD 70. Their SPIRITS had been in heaven, (absent from the body, present with the Lord), but as of that point in Revelation 15, no resurrected BODIES of mankind had yet ascended to heaven’s throne to be face to face with their Creator (as Christ affirmed in John 3:13).
Prior to that final glorious encounter before Gods throne in heaven, the dead bodies of the saints had to be changed by purification and made incorruptible, as I Cor. 15:53-54 tells us.
That purification of the saints’ bodies was where the symbolism of the “Sea of Glass” came in. This “Sea of Glass” in Revelation 15:2 was the heavenly original version in front of God’s throne by which its earthly counterpart in Moses’ tabernacle and Solomon’s Temple was patterned after. I am speaking of the laver in Moses’ tabernacle and the molten sea of polished brass in Solomon’s Temple Court.
Both the laver and the molten sea of polished brass contained water to be used by the priests to wash their hands and feet before entering the tabernacle, or before offering sacrifices on the altar. If the priests did not do so, they would die (Exodus 30:18-21). God’s requirement for this rite of purification was that serious. The main point being that absolute purity of body, soul, and spirit must be given to us, or we cannot live in God’s presence before His throne.
Here is where the “glass” term comes in for the laver and the “Sea of Glass”. Exodus 38:8 tells us “And he made the laver of brass, and the foot of it of brass, of the LOOKING-GLASSES of the women assembling, which assembled at the door of the tabernacle of the congregation.”
Mirrors in those days were made of highly polished brass, which provided the necessary reflective surface for a woman’s grooming. Undoubtedly, many of these brass looking-glass hand mirrors donated by the women for the tabernacle’s laver were given to the departing women of Israel by their Egyptian mistresses when they were thrust out of Egypt overnight. The people were so eager to see them leave that they urged them to go with presents of silver, gold, raiment, and whatever they asked for, thus “spoiling the Egyptians” (Exodus 12:33-36).
So, heaven’s temple and its “Sea of Glass” in Rev. 15:2 and 4:6 with clean water as clear as crystal was meant to be the original heavenly version depicted on earth by Moses’ tabernacle laver made out of the women’s brass looking-glasses, and also by Solomon’s molten sea of polished brass which held 2-3 thousand baths of water for the priests to purify themselves with.
In fact, most of the Revelation 15 chapter is a reflection of the OT ceremony of Solomon’s dedication of the Temple he built for the Lord (according to the pattern given by the Spirit to King David), which ceremony is found in II Chronicles 5-7, and I Kings 8. There are several significant elements duplicated from the OT dedication of Solomon’s temple and the NT scene before heaven’s throne presented in Revelation 15, as listed below:
THE SEA OF GLASS, WITH THE PRESENCE OF FIRE, RESULTING IN WORSHIP TO GOD
(OT) II Chron. 7:1 - At the temple dedication ceremony, King Solomon stood and then knelt on a brass scaffold in the middle of the court in front of the altar, with the molten SEA OF POLISHED BRASS on his right hand side in the south-eastern section of the court, offering his dedicatory prayer to God in that seventh month. “Now when Solomon had made an end of praying, the FIRE CAME DOWN FROM HEAVEN and consumed the sacrifices, and the glory of the Lord filled the house. And when the children of Israel saw how the FIRE CAME DOWN, and the glory of the Lord upon the house, they bowed themselves with their faces to the ground upon the pavement, and WORSHIPPED AND PRAISED THE LORD, saying, For he is good, for his mercy endureth forever.”
(NT) Rev. 4:5-6 - “And there were seven lamps of FIRE BURNING BEFORE THE THRONE, which are the seven Spirits of God. And before the throne there was a SEA OF GLASS like unto crystal: and in the midst of the throne, and round about the throne, were four beasts full of eyes before and behind...And when those beasts give glory and honor and thanks to him that sat on the throne, who liveth forever and ever, The four and twenty elders fall down before him that sat on the throne, and WORSHIP HIM that liveth forever and ever, and cast their crowns before the throne, saying, Thou art worthy, O Lord, to receive glory and honor and power, for thou hast created all things, and for thy pleasure they are and were created.”
(NT) Rev. 15:2-4 - “And I saw as if it were a SEA OF GLASS MINGLED WITH FIRE: and them that had gotten the victory over the beast...And they sing the song of Moses the servant of God, and the song of the Lamb, saying, Great and marvellous are thy works, Lord God Almighty; just and true are thy ways, thou King of saints. Who shall not fear thee, O Lord, and glorify thy name? for thou only art holy: for all nations shall come and WORSHIP BEFORE THEE; for thy judgments are made manifest.”
HARPS AND SINGING
(OT) II Chron. 5:12 - “Also the Levites which were the SINGERS, all of them of Asaph, of Heman, of Jeduthun, with their sons and brethren, being arrayed in white linen, having cymbals and psalteries and HARPS, stood at the east end of the altar, and with them an hundred and twenty priests sounding with trumpets:”
(NT) Revelation 15:2-3 - “And I saw as it were a sea of glass mingled with fire: and them that had gotten the victory over the beast, and over his image, and over his mark, and over the number of his name, stand on the sea of glass, having the HARPS of God. And they SING THE SONG of Moses the servant of God, and the song of the Lamb...”
THE EFFECT OF THE SMOKE OF GOD’S GLORY FILLING THE TEMPLE
(OT) II Chron. 7:1-2 - “Now when Solomon had made an end of praying, the fire came down from heaven, and consumed the burnt offerings and the sacrifices; and the GLORY OF THE LORD FILLED THE HOUSE. And THE PRIESTS COULD NOT ENTER INTO THE HOUSE OF THE LORD, because the glory of the Lord had filled the Lord’s house.”
(OT) I Kings 8:10-11 - “And it came to pass, when the priests were COME OUT OF THE HOLY PLACE, that the cloud filled the house of the Lord, so that the PRIESTS COULD NOT STAND TO MINISTER because of the cloud: for the GLORY OF THE LORD HAD FILLED THE HOUSE OF THE LORD.”
(NT) Revelation 15:6,8 - “And the seven angels CAME OUT OF THE TEMPLE, having the seven plagues, clothed in pure and white linen, and having their breasts girded with golden girdles...And the temple was FILLED WITH SMOKE FROM THE GLORY OF GOD, AND FROM HIS POWER; and NO MAN WAS ABLE TO ENTER INTO THE TEMPLE, till the seven plagues of the seven angels were fulfilled.”
There seem to be too many parallels between these two occasions in the OT and the NT for it to be merely coincidental. So it appears as if John’s NT Rev. 15 vision is another kind of dedication ceremony in the heavenly Temple in the AD 70 era, duplicating the OT type of ceremony at Solomon’s Temple dedication.
This heavenly ceremony culminated in heaven’s Temple being opened for access to the purified bodies of God’s “priests” - the resurrected saints - at the conclusion of the 7 plagues, when the time of the dead arrived for them to be judged and rewarded (just as in Rev. 11:18-19 when the temple was opened in heaven). No resurrected saints were allowed access to heaven’s Temple in their resurrected body forms until after the end of those 7 plagues (Rev. 15:6-8). That is when John finally shows us in Rev. 19:1-2 “MUCH *PEOPLE* IN HEAVEN” - ( NOT “souls” in heaven) “saying Alleluia; Salvation, and glory, and honor, and power, unto the Lord our God: For true and righteous are his judgments...”
I find the end of Solomon’s dedicatory prayer in II Chron. 6:41 in front of the Temple’s altar and the molten sea of polished brass to be quite prophetic. “Now therefore arise, O Lord, into thy resting place, thou, and the ark of thy strength: LET THY PRIESTS, O LORD GOD, BE CLOTHED WITH SALVATION, and let thy saints rejoice in goodness.” When each saint as a priest of God was finally “clothed” with the last phase of their salvation in AD 70, they had received their glorified, resurrected body made incorruptible; purified by the heavenly waters of that “Sea of Glass”, and made fit to stand rejoicing in God’s goodness before the fiery throne of God’s holy presence forevermore.