Augustine on the Incarnation

But "the light shines in darkness, and the darkness comprehended it not." Now the "darkness" is the foolish minds of men, made blind by vicious desires and unbelief. And that the Word, by whom all things were made, might care for these and heal them, "The Word was made flesh, and dwelt among us." For our enlightening is the partaking of the Word, namely, of that life which is the light of men. But for this partaking we were utterly unfit, and fell short of it, on account of the uncleanness of sins. Therefore we were to be cleansed. And further, the one cleansing of the unrighteous and of the proud is the blood of the Righteous One, and the humbling of God Himself; that we might be cleansed through Him, made as He was what we are by nature, and what we are not by sin, that we might contemplate God, which by nature we are not. For by nature we are not God: by nature we are men, by sin we are not righteous. Wherefore God, made a righteous man, interceded with God for man the sinner. For the sinner is not congruous to the righteous, but man is congruous to man. By joining therefore to us the likeness of His humanity, He took away the unlikeness of our unrighteousness; and by being made partaker of our mortality, He made us partakers of His divinity. For the death of the sinner springing from the necessity of comdemnation is deservedly abolished by the death of the Righteous One springing from the free choice of His compassion, while His single [death and resurrection] answers to our double [death and resurrection]. De Trinitate 4.2.4