Ezekiel 1:9

(Verses 8, 9) And they had four wings, and their wings were joined one to another. They did not turn back when they walked, but each one moved forward before its face. The Gospels are joined to each other and cling together, and they fly to and fro throughout the whole world, running here and there, without end to their flight, never surpassing or receding, but always proceeding to further things. And both Paul and Virgil say: Forgetting the things that are past, and reaching forth towards those things that are still to come.

"And they had faces and wings on four sides, and their wings were joined one to another." They have faces and wings in four directions, because in preaching throughout all regions of the world they demonstrate whatever they perceive concerning the humanity and whatever concerning the divinity of our Redeemer. For when they preach the incarnate God everywhere, they display their face in the four parts of the world. And when they announce that He is one with the Father and the Holy Spirit, they fly everywhere with the wing of contemplation. Their wings are joined one to another, because all their virtue and all their wisdom, by which they transcend other men through the flight of their contemplation, is mutually joined together in peace and unanimity. Hence it is written: The wisdom that is from above is first indeed pure, then peaceable. Hence also Truth says to these same preachers of His: Have salt in yourselves, and have peace among you. Therefore the wing of the living creatures is joined one to another, because the virtue and wisdom of the holy preachers is mutually united together in the peace of charity and concord. But the wing of one would be divided from another if, in that by which each one soars into wisdom, he refused to have peace with another. "They did not turn back when they went, but each one walked straight before its face." The feathered creatures, namely the holy preachers, when they advance, by no means turn back, because they pass from earthly actions to spiritual things in such a way that they are in no way turned back again to those things which they left behind. For to advance is, as it were, for them to go along a certain path, always moving in mind toward better things. On the contrary, it is said of the reprobate that they turned back in heart to Egypt. And Truth says through Himself: No one putting his hand to the plow and looking back is fit for the kingdom of God. For to put one's hand to the plow is, as it were, to open up the soil of one's heart through a certain plowshare of compunction for bringing forth fruit. But he looks back after the plow who, after the beginnings of good work, returns to the evils which he left behind. Because this by no means happens to God's elect, it is rightly now said through the prophet: They did not turn back when they advanced. He indicates why they do not turn back when he adds: "Each one…