John had earlier mentioned in Revelation 4:6 that he had seen “as it were a sea of glass,” located before God’s throne, having the function of a floor (see further Exodus 24:10; Ezekiel 1:22, Ezekiel 1:26). So pure was this floor that John needed a comparative to describe it; it was as it were a sea of glass—like crystal, he had explained in Revelation 4:6. In keeping with its nearness to God, its purity spoke of God’s glory, of the radically unworldly nature of whatever is heavenly. In the present passage John sees the same “sea of glass” (= floor), and again cannot find human words to describe what he sees and so must resort to a comparative: “what appeared to be” (“as” in Greek).
2 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.