The song was sung while the angels were coming out, with their plagues, who are therefore mentioned both before and after it, Revelation 15:1-6. And I saw as it were a sea of glass mingled with fire — It was before "clear as crystal," Revelation 4:6, but now mingled with fire, which devours the adversaries. And them that gained, or were gaining, the victory over the wild beast — More of whom were yet to come. The mark of the beast, the mark of his name, and the number of his name, seem to mean here nearly the same thing. Standing at the sea of glass — Which was before the throne. Having the harps of God — Given by him, and appropriated to his praise.
Related Commentaries of Revelation 15:2
Revelation 15:2
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.