God supposedly says in Leviticus 17:11:
“For the life of the flesh is in the blood, and I have given it for you on the
altar to make atonement for your souls.”
The text possibly arises from how it was noticed that a creature weakens and may die from loss of blood.
In the sacrificial system described in Leviticus, blood functions as a substitute. Instead of the worshiper’s life being forfeited, the animal’s life stands in its place. The shedding of blood marks that a life has been surrendered.
In several rituals, blood is placed on the altar or sanctuary objects. It seems that this symbolically “cleanses” or re-consecrates them. If so then because blood represents life, it symbolically counteracts death and impurity. We are told that this bleeding is not evil or glorifying violence but that it is symbolic theology. The message is supposedly that life is sacred, sin leads to death, reconciliation requires life to be offered and blood makes that invisible reality visible.
Jesus tacitly adopted such ideas when he said that if you offer an animal at the altar go and reconcile with enemies first then make the offering.