Hebrews 9:14, …how much more will the blood of Christ, who through the eternal Spirit offered Himself without blemish to God, purify our conscience from dead works to serve the living God.
The Law reveals that life is in the blood, which is why God required sacrifices for forgiveness and atonement (Leviticus 17:11). That life is in the blood is even true scientifically. According to the National Cancer Institute, “Blood is the fluid of life, transporting oxygen from the lungs to body tissue and carbon dioxide from body tissue to the lungs… Because it contains living cells, blood is alive. Red blood cells and white blood cells are responsible for nourishing and cleansing the body. Without blood, the human body would stop working.” You literally need blood to be alive. Without blood, you’d die.
Thus, God required blood to keep His people spiritually alive. Just as blood cleanses our bodies physiologically, so sacrificial blood proved the necessity for spiritual cleansing in God’s sight (v. 13). Yet these were never enough. Certainly, the blood of goats, bulls, and heifers sanctified the flesh, as God’s Law required. Even more, then, Christ’s own blood makes full and complete purification for our souls, “once for all” (10:1-10). This He did of His own volition, that His own holy and unblemished blood would make perfect atonement for our souls.
National Cancer Institute, “Cancer Registration & Surveillance Modules, Anatomy & Physiology, Cardiovascular System, Blood,” accessed July 17, 2020, https://training.seer.cancer.gov/anatomy/cardiovascular/blood/#:~:text=Blood%20is%20the%20fluid%20of,body%20tissue%20to%20the%20lungs.&text=Because%20it%20contains%20living%20cells,human%20body%20would%20stop%20working.