Hebrews 9:14 How much more, then, will the blood of Christ, who through the eternal Spirit offered himself unblemished to God, cleanse our consciences from acts that lead to death, so that we may serve the living God!
When the people of the Old Testament offered the blood of various animals in sacrifice, it was to ceremonially cleanse them of their sins.
In others words, this was to allow others to see they were willing to be washed by blood because God wanted that.
When Jesus paid for our sins with His own blood, it was a final and permanent sacrifice to cleanse our bodies and souls once and for all!