They Sing - Revelation 15:1-4

Revelation 15:1-4 ESV 

Then I saw another sign in heaven, great and amazing, seven angels with seven plagues, which are the last, for with them the wrath of God is finished.

And I saw what appeared to be a sea of glass mingled with fire—and also those who had conquered the beast and its image and the number of its name, standing beside the sea of glass with harps of God in their hands.

And they sing the song of Moses, the servant of God, and the song of the Lamb, saying,

“Great and amazing are your deeds,

O Lord God the Almighty!

Just and true are your ways,

O King of the nations!

Who will not fear, O Lord,

and glorify your name?

For you alone are holy.

All nations will come

and worship you,

for your righteous acts have been revealed.”

The next sign is in heaven. The sea of glass represents the change of the waters of the deep which were dark and turbulent in the beginning. The sea in heaven reflects the peace and purity of God, which is imparted by the fiery presence of the Holy Spirit. 

It is this Spirit Who enables the unity of the song of Moses and the song of the Lamb to be sung as one song.