3 occurrences in 3 dictionaries

Reference: Sea of Glass

Easton

a figurative expression used in Re 4:6; 15:2. According to the interpretation of some, "this calm, glass-like sea, which is never in storm, but only interfused with flame, represents the counsels of God, those purposes of righteousness and love which are often fathomless but never obscure, always the same, though sometimes glowing with holy anger." (Comp. Ps 36:6; 77:19; Ro 11:33-36.)

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Hastings

One of the features of the heavenly landscape described in Re 4:6; 15:2. By its side stood those who had been victorious in the struggle with the beast, singing to the glory of God. Its location was apparently before the throne of God. Just what the symbolism here intended is, it is difficult to state. The probability is, however, that there is no distinct symbolism whatever, but that the reference is rather to the brilliancy of the waters as one element in the supremely beautiful land of heaven.

Shailer Mathews.

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Morish

Symbolical laver seen in heaven, signifying fixed, accomplished holiness, with no need of the hands or feet being washed. Re 4:6. In Re 15:2 the saints are seen standing upon 'a sea of glass mingled with fire': they had come out of the tribulation.

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