And 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 living creatures full of eyes in front and behind.
All Commentaries on Revelation 4:6 Go To Revelation 4
Victorinus of Pettau
AD 303
That is the gift of baptism which He sheds forth through His Son in time of repentance, before He executes judgment. It is therefore before the throne, that is, the judgment. And when he says a sea of glass like to crystal, he shows that it is pure water, smooth, not agitated by the wind, not flowing down as on a slope, but given to be immoveable as the house of God.