Since ancient times, blood was used as a ritual sacrament. It was seen as the carrier of the spirit of life and character that lived in a person. Blood has been symbolic of the seat of the soul and the life force within a person.
In our culture, we use the term “blood” in symbolic ways, employing idiomatic expressions like: blood money; sweat blood; blood on one’s hands; blood out of a stone; bleed someone white; blood brother.
Without the shedding of blood
The Bible tells us that transgressions and sins cannot be forgiven without blood. It is the shedding of blood that makes forgiveness possible.
All things are cleansed with blood, and without the shedding of blood there is no forgiveness (Hebrews 9:22).
God’s covenants with humanity required blood
Both of God’s covenants with humanity required blood. During the Old Testament period, the blood of sacrificial animals was accepted as a way to resolve sins. But this had only a temporary effectiveness, because it was required yearly.
The first covenant was not inaugurated without blood. Moses took the blood of the calves and the goats … and sprinkled … the people, saying, “This is the blood of the covenant which God commanded you” (Hebrews 9:19-20).
Through His work on the cross, Jesus Christ made possible another way to pay the debt caused by mankind’s transgressions against His divine law. Instead of requiring the blood of an animal or the blood of the transgressor, God provided a more radical way—the giving of the blood of His only begotten Son.
For the Law [of Moses] made nothing perfect, and on the other hand there is a bringing in of a better hope through which we draw near to God … Jesus has become the guarantee of a better covenant (Hebrews 7:19, 22)
Now the God of peace, who brought up from the dead the great Shepherd of the sheep through the blood of the eternal covenant, even Jesus our Lord … (Hebrews 13:20).
Where do you get blood?
We need blood in order to forgive the people who sinned against us. But where do you get it? Is the blood of Jesus 
enough? Or do you need to activate the “eye for an eye” method and make the people who hurt you pay for their failures in some way?
For the life (soul) of the flesh is in the blood, and I have given it to you on the altar to make atonement for your souls, for it is the blood by reason of the life (soul) that makes atonement (Leviticus 17:11).