Question: "What is the sea of glass mentioned in Revelation 4:6 and 15:2?"
Answer: Twice in the book of Revelation, John mentions a “sea of glass” near the throne of God. John does not elaborate much about what this sea of glass actually is. Is it water that looks like glass? Is it smooth or rough like broken glass? Does it move like the waves of the sea, or is it stationary? As we know it, the sea is a dynamic, moving force, but “glass” gives the impression of stillness. How can a sea be made of glass? What is John talking about?
Revelation 4:6 says, “Before the throne there was as it were a sea of glass, like crystal.” And Revelation 15:2 says, “I saw what appeared to be a sea of glass mingled with fire.” In neither verse does John say that he saw a literal sea of glass; rather, he says, “There was as it were a sea of glass” and “I saw what appeared to be a sea of glass.” The words of comparison make a big difference. It is one thing to say you were struck by lightning; it is quite another thing to say you feel as if you were struck by lightning.
Apparently, what John saw was impossible to describe – it was so different from anything he had seen that he was compelled to describe it using a contradictory statement. Expressing the inexpressible may demand an oxymoron. Whatever John saw, it obviously had qualities both of the sea and of glass. Perhaps it had the sea’s motion and expanse and glass’s transparency and purity. Add to that the words “crystal” and “mingled with fire,” and chances are that John was trying to convey the vivid brilliance, vast expanse, and lucid purity of what he saw.
Daniel’s vision of four beasts. Ezekiel’s vision of wheels with eyes. John’s vision of a sea of crystalline glass. Any time the prophets described visions of the spiritual world, they were forced to use metaphorical language, and that can be confusing. Finite human language cannot fully describe infinite things. The human mind is too limited to apprehend all the realities of the spiritual realm. But we have this confidence: the prophets and apostles wrote under the inspiration of the Holy Spirit, and the words they chose are the best possible communication. Daniel, Ezekiel, and John faithfully described what they saw, and we must faithfully attempt to “decode” their descriptions. For now, we see “through a glass darkly,” and, to a certain degree, the “sea of glass” and other heavenly verities will remain mysteries – until we see them for ourselves with glorified eyes and minds.