Jerome

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.

Commentary on Ezekiel ↗

Gregory the Dialogist

"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. …

Homilies on Ezekiel, Book 1, Homily 3 ↗