John Calvin Commentary Genesis 22:13

"And Abraham lifted up his eyes, and looked, and behold, behind [him] a ram caught in the thicket by his horns. And Abraham went and took the ram, and offered him up for a burnt-offering in the stead of his son." — Genesis 22:13 (ASV)

And, behold, behind him a ram. What the Jews fabricate concerning this ram, as having been created on the sixth day of the world, is like the rest of their fictions. We do not need to doubt that it was presented there by miracle, whether it was then first created or brought from some other place; for God intended to give his servant what would enable him, with joy and cheerfulness, to offer up a pleasant sacrifice, and at the same time, he admonishes him to give thanks. Moreover, since a ram is substituted in place of Isaac, God shows us, as in a mirror, what is the purpose of our mortification; namely, that by the Spirit of God dwelling within us, we, though dead, may yet be living sacrifices. I am aware that more subtle allegories may be elicited, but I do not see on what foundation they rest.