An animal selected for sacrifice had to be “without defect or blemish” (Leviticus 22:21)—it couldn’t be blind, wounded, sick, malnourished or imperfect in any way. A person was not permitted to drag an already-dead animal to the altar and present it before God. After all,
that dead animal might have died for any number of reasons other than as a sacrifice for sin. It might have been poisoned or starved to death, drowned or been accidentally killed (be it by a person or another animal), or it might have died of some sickness. The animal had to be in excellent health, not just because God was worthy of the very best, but because there needed to be no misunderstanding about how and why the animal had died. In ritual sacrifice, the animal had to be purposefully and deliberately killed and its fresh blood poured on the altar by a priest as an acknowledgement of that person’s sin and spiritual indebtedness to God.