“In the Old Testament
The image of the four animals originates from the prophetic vision of Ezekiel (Ezekiel 1:4-28; also 10:14 and 41:19). Ezekiel describes these creatures as follows:
“The appearance of them was like a man; and every one had four faces, and every one had four wings; and their legs were straight, and the soles of their feet were like the sole of a calf’s foot: and they sparkled like burnished brass. And they had the hands of a man under their wings on their four sides; <...> Their faces looked like a man’s face, and the face of a lion on the right side of all four; and on the left side, the face of a calf for all four, and the face of an eagle for all four. Their faces and their wings were divided above; each had two wings touching one another, and two wings covered their bodies. <...> On the earth beside these creatures, there was one wheel for each of the four faces. <...> And their rims were high and dreadful; and the rims of all four were full of eyes round about.” — Ezekiel 1:5-18
Later (Ezekiel 10:1), these beings are called cherubim (cf. 1 Chronicles 28:18), and instead of the face of a calf, Ezekiel mentions the face of a cherub.
In the New Testament
The Apostle John in Revelation, chapter 4, continued this tradition, however, speaking of one face for each of the four creatures:
“...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. And the first beast was like a lion, and the second beast like a calf, and the third beast had a face as a man, and the fourth beast was like a flying eagle. And the four beasts had each of them six wings about him; and they were full of eyes within: and they rest not day and night, saying, Holy, holy, holy, Lord God Almighty, which was, and is, and is to come.”
Later in John’s account of the Lamb opening the seals of the Book of Life, each of the four beasts, upon opening the first four seals, says “Come and see,” after which John sees the four horsemen of the Apocalypse one by one.
In the Apocrypha