From the Catena on Genesis.
In place of Isaac the just, a ram appeared for slaughter, in order that Isaac might be liberated from his bonds. The slaughter of this animal redeemed Isaac from death. In like manner, the Lord, being slain, saved us; being bound, He loosed us; being sacrificed, He redeemed us...
For the Lord was a lamb, like the ram which Abraham saw caught in the bush Sabec. But this bush represented the cross, and that place Jerusalem, and the lamb the Lord bound for slaughter.
For as a ram was He bound, says he concerning our Lord Jesus Christ, and as a lamb was He shorn, and as a sheep was He led to the slaughter, and as a lamb was He crucified; and He carried the cross on His shoulders when He was led up to the hill to be slain, as was Isaac by his father. But Christ suffered, and Isaac did not suffer: for he was but a type of Him who should suffer. Yet, even when serving only for a type of Christ, he smote men with astonishment and fear.
For a new mystery was presented to view, -- a son led by his father to a mountain to be slain, whose feet he bound together, and laid him on the wood of the sacrifice, preparing with care whatever was necessary to his immolation. Isaac on his part is silent, bound like a ram, not opening his mouth, nor uttering a sound with his voice. For, not fearing the knife, nor quailing before the fire, nor troubled by the prospect of suffering, he sustained bravely the character of the type of the Lord. Accordingly there lies Isaac before us, with his feet bound like a ram, his father standing by, with the knife all bare in his hand, not shrinking from shedding the blood of his son.