God can’t be around sin. Think of it like an unblemished white crystal. Can’t have black. Same goes for the sacrifice. Unblemished. No sin. Christ.
Now, the sacrifice. Without getting too granular on which kind of animal was used and why, nevertheless, the writer of Hebrew (9:12-18) sums up what Leviticus 17:11 states:
“For the life of the flesh is in the blood, and I have give it to you upon the altar to make atonement for your souls; for it is the blood that makes atonement for the soul.”
The high priest sprinkles the blood of the animal over the altar in the holy of holies, a place in the temple only he can enter. And even then, it’s an iffy exercise because he can get killed if he didn’t wash up correctly. God is serious. The whole system of every sacrificial duty is marginally specific and narrow, errors are severely dealt with. He cannot be around sin. Blood gets sprinkled, Israel’s sins are good for a year. Wash, rinse, repeat.
Further, the holy of holies is a sacred space in the temple, and perhaps, world. It’s a place where God and man convene together. God spells out to the Israelites a way to have this meeting. It’s very specific and any screw up, likely results in the death of somebody. Without a death “for death,” the high priest can never convene with God.
Why all this death? Herald back. God and Adam/Eve are in the garden. What is that place? How can they (God and man) both be together and they’re not dead? The tree of life. This is God’s room. Adam and Eve, without the tree of life, can’t “live forever.” It’s right there in the text. They’re not immortal because they haven’t sinned yet, they’re immortal because they are in the presence of the tree of life, feeding from it. God is there. Everything is awesome. But they “sin” and lose privileges to the tree of life, and will die. Paul said, death is the result of sin. End of. Hence, death for a death. In the ancient world, this came in the form of animal sacrifice. Why? God told Adam to what after he was kicked out? (cf. the Book of Jubilees). Sacrifice a bunch of animals for their sin. What did Noah do when he landed on dry land? Sacrifice a bunch of animals. Death for death. And. Death for life. The system evolves over time, and the Israelites are the torchbearers for the one, true God. Unfortunately, they weren’t supposed to do a great job anyway because, well, they couldn’t, because they can’t. They sin too much. Everyone does. Whether it’s murder or a white lie. None of it is good, right? Not to mention pouring lighter fluid down the stem of an ant hill and dropping match in there isn’t too cool either, I would assume. But, we all remember some kid like that when we were young. Or was it you?!!
In comes Jesus Christ. Unblemished, how? He’s God, in human form. The hypostatic union. God, by design, was the only one who could remedy this”sin” problem. But, only by following His program. He sins not. And he seems to be completely human. But only God cannot sin. Hence. So. They. Know. He’s. God. He stirs up things during one of the most religious times of year, gets arrested and dies on a weekend that’s pretty symbolic of that whole atonement-sacrificial sin-thing, then an earthquake shakes everything for a bit and the curtain dividing the holy of holies and the rest of the temple rips open. Then of all things, a generation later that whole temple gets completely destroyed. No more sacrificial system.
The sacred space is now..? Not Christ. No, he was the sacrifice, the one put in place for you, the holy of holies. You are sacred space, and the blood has been sprinkled on you. God sees no sin in you, thus He can convene with you because you are sacred space.