From Revelation 4 (KJ21):
6 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 beings full of eyes in front and behind.
7 And the first being was like a lion, and the second being like a calf, and the third being had the face of a man, and the fourth being was like a flying eagle.
8 And each of the four living beings had six wings about him, and they were full of eyes within; and they rested not day and night, saying, “Holy, holy, holy, Lord God Almighty, who was, and is, and is to come!”
What do these four living beings represent?