3 There is therefore a Light which made this light of the sun: let us love this Light, let us long to understand it, let us thirst for the same; that, with itself for our guide, we may at length come to it, and that we may so live in it that we may never die. This is indeed that Light of which prophecy long ago going before thus sang in the psalm: “O Lord, You shall save men and beasts; even as Your mercy is multiplied, O God.” These are the words of the holy psalm: mark ye what the ancient discourse of holy men of God did premise concerning such a light.
“Men,” says it, “and beasts You shall save, O Lord; even as Your mercy is multiplied, O God.” For since You are God, and hast manifold mercy, the same multiplicity of Your mercy reaches not only to men whom You have created in Your own image, but even to the beasts which You have made subservient to men. For He who gives salvation to man, the same gives salvation also to the beast. Do not blush to think this of the Lord your God: nay, rather believe this and trust it, and see thou think not otherwise.
He that saves you, the same saves your horse and your sheep; to come to the very least, also your hen: “Salvation is of the Lord,” and God saves these. You are uneasy, you question, I wonder why you doubt. Shall He disdain to save who deigned to create? Of the Lord is the saving of angels, of men, and of beasts: “Salvation is of the Lord.” Just as no man is from himself, so no man is saved by himself. Therefore most truly and right well does the psalm say, “O Lord, You shall save men and beasts.” Why? “Even as your mercy is multiplied, O God.” For You are God, You have created, You save: You gave being, You give to be in health.
Source: Tractates on the Gospel of John (New Advent)