Sea of Glass

Concise Bible Dictionary:

Symbolical laver seen in heaven, signifying fixed, accomplished holiness, with no need of the hands or feet being washed (Rev. 4:66And before the throne there was a sea of glass like unto crystal: and in the midst of the throne, and round about the throne, were four beasts full of eyes before and behind. (Revelation 4:6)). In Revelation 15:2 The saints are seen standing upon “a sea of glass mingled with fire;” they had come out of the tribulation.