Revelation 15:2

And I saw what seemed to be an ocean of glass, mixed with fire, and those who had been victorious over the beast, his statue and the number of his name. They were standing beside [or, "on"] the ocean of glass and held harps [given to them] by God.

Revelation 4:6

And there was an ocean, as crystal-clear as glass, in front of the throne. And at the center, surrounding the throne were four living beings, covered with eyes in the front and back of them. [Note: In view of Isa. 6:1-3 and especially Eze. 10:20ff, these "living beings" appear to be some special order of heavenly beings who inhabit the presence of God].

Revelation 5:8

And when He had taken the book, the four living beings and the twenty-four elders fell down in front of the Lamb [i.e., to worship Him]. Each one of them held [in his hands] a harp and a golden bowl full of incense, which are the prayers of the saints [See Psa. 141:2; Rev. 8:3-4].

Revelation 12:11

And they [i.e., the brothers. See 6:9-11] gained the victory over Satan by the blood of the Lamb, and by [remaining true to] the message of their testimony. And they did not love their lives [so much that they refused] to die [for their faith].

Revelation 21:18

The material for the city's wall was jasper, and the city [itself] was made of pure gold, as clear as glass.

Matthew 3:11

"I certainly am immersing you in water following [your] repentance, but the One who follows my [ministry], whose sandals I do not deserve to remove [as His slave], will immerse you people with the Holy Spirit and with fire [i.e., the punishment in hell. See verses

1 Peter 1:7

But these will only test your faith, which is more valuable than gold which, though refined by fire, eventually perishes. Your faith, [however], will [endure and eventually] prove to be praiseworthy and honorable when Jesus returns.

1 Peter 4:12

Loved ones, do not be surprised that you people are undergoing extremely difficult trials, as though something strange were happening to you, for it is [only] a test [of your faith].

Revelation 11:11-12

And after three and a half days, God breathed life into them and they stood up on their feet, and the people who saw them became terrified.

Revelation 13:14-5

[And] by being given [power] to perform these signs in the sight of the [first] beast, he deceived the people on earth. He told them to make a statue to [honor] the [first] beast, who had been wounded by a sword and yet lived [through it].

Revelation 19:1-7

After these things I heard what sounded like the loud voices of a huge crowd in heaven, shouting, "Hallelujah [which means, "Praise God"]! Salvation and splendor and power belong to our God.

Treasury of Scripture Knowledge

Summary

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.

Bible References

A sea

Revelation 4:6
And there was an ocean, as crystal-clear as glass, in front of the throne. And at the center, surrounding the throne were four living beings, covered with eyes in the front and back of them. [Note: In view of Isa. 6:1-3 and especially Eze. 10:20ff, these "living beings" appear to be some special order of heavenly beings who inhabit the presence of God].
Revelation 21:18
The material for the city's wall was jasper, and the city [itself] was made of pure gold, as clear as glass.

Mingled

Matthew 3:11
"I certainly am immersing you in water following [your] repentance, but the One who follows my [ministry], whose sandals I do not deserve to remove [as His slave], will immerse you people with the Holy Spirit and with fire [i.e., the punishment in hell. See verses
1 Peter 1:7
But these will only test your faith, which is more valuable than gold which, though refined by fire, eventually perishes. Your faith, [however], will [endure and eventually] prove to be praiseworthy and honorable when Jesus returns.
1 Peter 4:12
Loved ones, do not be surprised that you people are undergoing extremely difficult trials, as though something strange were happening to you, for it is [only] a test [of your faith].

That had

Revelation 11:11
And after three and a half days, God breathed life into them and they stood up on their feet, and the people who saw them became terrified.
Revelation 12:11
And they [i.e., the brothers. See 6:9-11] gained the victory over Satan by the blood of the Lamb, and by [remaining true to] the message of their testimony. And they did not love their lives [so much that they refused] to die [for their faith].
Revelation 13:14
[And] by being given [power] to perform these signs in the sight of the [first] beast, he deceived the people on earth. He told them to make a statue to [honor] the [first] beast, who had been wounded by a sword and yet lived [through it].
Revelation 14:1
And I looked, and there in front of me was the Lamb, standing on Mount Zion, and with him were one hundred and forty-four thousand persons, with the Lamb's name and His Father's name written on their foreheads.

Having

Revelation 5:8
And when He had taken the book, the four living beings and the twenty-four elders fell down in front of the Lamb [i.e., to worship Him]. Each one of them held [in his hands] a harp and a golden bowl full of incense, which are the prayers of the saints [See Psa. 141:2; Rev. 8:3-4].
Revelation 14:2
And I heard a sound from heaven like the roar of much rushing water, and like the sound of loud thunder. And the sound I heard was like people playing their harps.
Revelation 19:1
After these things I heard what sounded like the loud voices of a huge crowd in heaven, shouting, "Hallelujah [which means, "Praise God"]! Salvation and splendor and power belong to our God.