Revelation 4:6-8

Something like a sea of glass, similar to crystal, was also before the throne. Four living creatures covered with eyes in front and in back were around the throne on each side. The first living creature was like a lion; the second living creature was like an ox; the third living creature had a face like a man; and the fourth living creature was like a flying eagle. Each of the four living creatures had six wings; they were covered with eyes around and inside. Day and night they never stop, saying, Holy, holy, holy, Lord God, the Almighty, who was, who is, and who is to come.