The Harp-Playing Victors on the Sea of Glass

I saw as it were a sea of glass mingled with fire, and those who had overcome the beast, and its image, and the number of its name, standing on the sea of glass, having the harps of God, and singing the canticle of Moses, the servant of God, and singing the canticle of the Lamb. (Apocalypse 15:2-3)

Before the angels empty their vessels on the earth, John sees pious and righteous people singing the "canticle of the Lamb." Red flames dot the sea of glass mentioned in the text, and a man in the middle holds a scroll up to the Lamb. The words of the canticle appear on the scroll: Magna et mirabilia op[er]a tua Domine D[eu]s om[ni]p[oten]s iuste e[t] vere vie tue rex seculor[um](Great and wonderful are your works, Lord God almighty; just and true are your ways, king of ages).