Revelation 4:6, 8

and before the throne there was as it were a sea of glass, like crystal. And around the throne, on each side of the throne, are four living creatures, full of eyes in front and behind

And the four living creatures, each of them with six wings, are full of eyes all around and within, and day and night they never cease to say, “Holy, holy, holy, is the Lord God Almighty, who was and is and is to come!”