Blood is a very vital element of a creature’s life. In both the Old and New Testaments, it is not just a biochemical component of life, but its mention often has a symbolical and functional purpose. The shedding of blood between animals is not considered murder but a means of survival, whether for defense or food. But it is very much different when human blood is shed. Murder does not just hold moral and legal consequences but spiritual consequences as well since God values human life. In Genesis 9:5-6, God requires the blood of anyone who takes another person’s life, and even a wild animal must die if it kills a person, as human beings are made in God’s own image. The first instance of murder mentioned in the Bible is in Genesis 4:1-15, concerning the brothers Cain and Abel. God then cursed Cain for murdering his brother Abel. Here, Abel’s blood cried out to God from the ground, and God exacted vengeance against Cain by cursing him. God will always bring justice against those who shed the blood of others.
Abel’s murder was the first mention of human bloodshed in the Bible, but his blood was not the first to be shed out of all creatures. After the fall of man, God made garments of skin to cover Adam and Eve’s nakedness (Genesis 3:21 Unto Adam also and to his wife did the Lord God make coats of skins, and clothed them.). God said that if they ate from the forbidden tree, they would surely die (Genesis 2:15-17). But man did not die immediately; instead, there was the shedding of blood when God made the garments of skin from an innocent creature to cover our shame. That was probably the precursor of animal sacrifice for the atonement of man’s sin. As written in (Hebrews 9:22 And almost all things are by the law purged with blood; and without shedding of blood is no remission.), there is no forgiveness without the shedding of blood, according to the Mosaic law and according to Leviticus 17:11:
“For the life of the flesh is in the blood: and I have given it to you upon the altar to make an atonement for your souls: for it is the blood that maketh an atonement for the soul.”
Since man has to die for his/her sins, God made a way so that God’s people in the old covenant could make atonement by allowing the blood of animals to be the substitute for our own blood.
Another use of blood in the Old Testament involves entering into a covenant by blood. God made an unconditional blood covenant with Abraham in Genesis 15:7-21, with the promise of countless descendants, a vast and bountiful land, and blessings. The covenant was done in an ancient Near Eastern ritual of sealing promises. God told Abraham to bring Him a three-year-old heifer, a goat, and a ram, as well as a dove and pigeon. Each animal was cut in half, except for the birds, and laid down. To seal the promise, God – not Abraham –passed between the pieces as a way of saying, “May I become like these animals if I don’t keep my promise.” God bound himself in the covenant with Abraham without requiring anything from Abraham. That means that if God does not keep His promises, He must die or cease to be the immortal God. It is amazing how God would put Himself at risk just to show how sure He would keep His promise to man. This covenant was later amplified through the covenant sacrifice of Jesus Christ (Hebrews 8:6 But now hath he obtained a more excellent ministry, by how much also he is the mediator of a better covenant, which was established upon better promises.).
In the blood sacrifice of Christ upon the cross, we receive the New Covenant (Luke 22:20 Likewise also the cup after supper, saying, This cup is the new testament in my blood, which is shed for you.). Even if mankind did not fulfill its end of the covenant, God took it upon Himself by sending His one and only Son to die for us (John 3:16). Unlike the blood of Abel, which cried out for vengeance, the blood of Christ cries out for our forgiveness and restoration (Hebrews 12:24). The animal blood sacrifices were never enough to forgive man’s sins but just an annual reminder of the ugliness of sin. As Hebrews 10:4 says, “For it is not possible that the blood of bulls and of goats should take away sins.” The sacrifices in the Old Testament were merely the foreshadowing of the ultimate blood sacrifice of Christ, once and for all. In Christ, the atonement for man’s sin was made complete and was fully paid by His blood when He gave up His life on the cross and cried out, “It is finished (John 19:30).”
“Being justified freely by his grace through the redemption that is in Christ Jesus:  Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God.”
(Romans 3:24-25 KJV)