The wheel within a wheel is, as we said, the New Testament within the Old Testament, because what the Old Testament defined, the New showed forth. To cut a long story short, why is that Eve was brought forth while Adam slept save that the Church was created through Christ’s death? Why is it that Isaac was led to sacrifice carrying the wood, placed on the altar and lives, save that Our Savior, led to His Passion, Himself carried the wood of His Cross? And thus He died in sacrifice for us in His humanity that He might remain immortal through His divinity. Why is it that the acquitted manslayer returns to his own after the death of the high priest (see Num. 35:25), unless the human race, which by sinning incurred death, after the death of the True High Priest, namely, Our Savior, is freed from the fetters of its sins and restored to possession of Paradise? Why is it that the mercy seat is ordered to be made in the Tabernacle, above which two Cherubim of purest gold are placed, one on one end, the other on the other end, spreading their wings and covering the mercy seat, who each look to one another with their faces turned toward the mercy seat, save that each Testament thus accords with itself regarding the Mediator of God and men, that what the one defines, the other shews forth? For what is meant by the mercy seat save the very Savior of the human race? Of Him it is said through Paul: “Whom God set forth to be a propitiation through faith in His blood” (Rom. 3:25). But what is meant by the two Cherubim which are described as the fullness of learning if not both Testaments? One of them stands at one end of the mercy seat, the other indeed at the other end, because what the Old Testament began by prophecy to promise concerning the Incarnation of Our Savior, the New Testament perfectly tells fulfilled. Truly the two Cherubim are made from purest gold because the two Testaments are described in pure and simple truth. They assuredly spread their wings and cover the mercy seat because we who are the mercy seat of Almighty God are protected from impending sins by the edification of Holy Writ. While we carefully consider its sayings we are veiled by its wings from the error pf ignorance. Truly the two Cherubim look toward each other with their faces turned to the mercy seat because both Testaments are in no way discordant with themselves. And they, as it were, again turn their faces to themselves because what the one promises the other shows forth when they see the Mediator of God and men placed between them. But the Cherubim would turn their faces from their own selves if the one Testament refuted what the other promised. But when they speak in accord concerning the Mediator of God and men, so that they again gaze at each other, they face towards the mercy seat. Therefore the wheel is in the midst of a wheel because the New Testament is encompassed by the Old. And, as we have often said already, what the Old Testament promised the New showed forth, and what the one covertly announced the other openly proclaimed manifest. Therefore the Old Testament is the prophecy of the New, and the New is the exposition of the Old.

St. Gregory the Great, Homilies on the Book of the Prophet Ezekiel, VI:15, trans. Theodosia Gray, Etna, CA: Center for Traditionalist Orthodox Studies, 1990, p. 60-61.