Hebrews 9:15-22
15Therefore he is the mediator of a new covenant, so that those who are called may receive the promised eternal inheritance, since a death has occurred that redeems them from the transgressions committed under the first covenant. 16For where a will is involved, the death of the one who made it must be established. 17For a will takes effect only at death, since it is not in force as long as the one who made it is alive. 18Therefore not even the first covenant was inaugurated without blood. 19For when every commandment of the law had been declared by Moses to all the people, he took the blood of calves and goats, with water and scarlet wool and hyssop, and sprinkled both the book itself and all the people, 20saying, “This is the blood of the covenant that God commanded for you.” 21And in the same way he sprinkled with the blood both the tent and all the vessels used in worship. 22Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins.

The concept of mediation is found throughout the Bible. The only time we see no one or nothing serving as mediator is found in the Garden of Eden with Adam and Eve before The Fall. The holiness of God is so great, none of us can stand in His presence with mediation. We are not worthy. Even after Adam’s fall into sin, an animal was killed to cover their shame.

Throughout the Old Testament, there are several things/people who mediate between God and man.
1. The blood of that first killed animal was only the beginning. Abraham tried to stand between God and the people of Sodom and God tried to be generous, but the sin of Sodom was too great.
2. Joseph stands between his brothers and starvation in Egypt.
3. Moses was allowed by God to stand between Him and the people with numerous interesting consequences. It began when God hid Moses in the cleft of a rock and passed before him, allowing Moses to see “His back side.” Even Moses was not allowed to see the full glory of God. But he did intercede for the people when they chose idolatry over God.
4. The blood of the Passover lamb stood between The Children of Israel and the death of the firstborn during the plagues in Egypt.

The list can go on, but you get the point. God is approached via a mediator for He is pure holiness. Blood has always played a part in that process. These verses from Hebrews remind us of Moses use of a blood offering to sanctify the people of Israel. But that was a temporary fix, held in place by the mercy of God. He accepted that offering because it foreshadowed the final sacrifice made by Jesus. I doubt if Moses had any inclination whatsoever about that horrific sacrifice Jesus would have to make, but he knew enough to be obedient to God’s commands. He knew that there would have to be a significant shedding of blood to seal the forgiveness covenant, for without the shedding of blood there is no forgiveness of sins.