Revelation 15:2: 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.

After John saw the sign of the Son of Man at the start of the Third Woe in Revelation 15:1,¹ he saw a sea of glass mingled with fire.² This image represents the glory of God's celestial kingdom³ as it will appear after all exaltation-worthy saints⁴ have been gathered to stand with Christ on mount Zion at the end of the Second Woe in Revelation 14:14-16.⁵ In other words, John saw God's glorified celestial residence⁶ which had the appearance of a sea of glass mingled with fire.⁷ He did not see this earth as a fiery sea of glass because this earth will still be a fallen telestial earth during the future Third Woe before the millennium.⁸ After the millennium, this earth will die and will be resurrected.⁹ Only then will the earth have the appearance of a sea of glass mingled with fire like God's celestial residence.¹⁰

The image of all exaltation-worthy saints on the sea of glass symbolizes their preservation in heaven¹¹ against the fiery judgments¹² on earth during the Third Woe.¹³ These saints in heaven are redeemed and have their calling and election made sure.¹⁴

John's vision of the sea of glass mingled with fire is similar to his vision of celestial paradise in Revelation chapters 4 and 5.¹⁵ However, the two visions are completely distinct in their timing and meaning.¹⁶ In Revelation 4 and 5, John saw celestial-worthy disembodied spirits in paradise who were waiting for their resurrection to the celestial kingdom at the time of John's vision in 96 AD.¹⁷ In Revelation chapter 15, John saw exaltation-worthy people that had been transfigured, translated,¹⁸ or resurrected to God's celestial kingdom¹⁹ at the start of the Third Woe that still lies in the future.²⁰

In John's vision of the future Third Woe, he specifically saw redeemed saints in heaven who endure the Great Tribulation²¹ and have gotten the victory over the beast, and over his image, and over his mark, and over the number of his name.²² The beast in this verse refers to the Second Beast identified in Revelation 13:11-16.²³ These saints gained their victory over the beast²⁴ because they made gospel covenants,²⁵ including temple covenants for themselves or vicariously. They are those who remain steadfast and immovable on earth or in heaven until the morning of the first resurrection when they will stand with Christ on mount Zion as translated, transfigured, or resurrected people.²⁶ They refuse to conform their lives to the worldly image of the beast²⁷ and in this way they overcome²⁸ his mark and the number of his name, which is 666.²⁹

These exaltation-worthy saints will stand on the sea of glass³⁰ after Christ gathers them as wheat or grapes during the initial harvest at the end of the Second Woe as recorded in Revelation 14:14-16.³¹ The same saints seen on the sea of glass are the 144,000 Servants that stand with Christ on heavenly mount Zion.³² In other words, the sea of glass mingled with fire in Revelation 15:2 is symbolically synonymous with heavenly mount Zion that John saw in Revelation 14:1-2. Even though heavenly mount Zion is depicted in this vision as a sea of glass, it is solid and firm.³³ Hell, by contrast, is like the turbulent sea from which the First Beast arose in Revelation 13:1³⁴ and like the many waters of chaos that support the Great Whore in Revelation 17:1.³⁵

The 144,000 Servants have harps of God,³⁶ which accompany their songs of praise.³⁷ These harps cannot be equaled by any earthly instruments,³⁸ nor can they be played by anyone unworthy of exaltation in the celestial kingdom.³⁹