Sea of glass

a figurative expression used in Rev. 4:6 and 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." (Compare Ps. 36:6; 77:19; Rom.
11:33-36.)