Down through history, friends, especially children, would make little cuts on their arms, then join them together arm to arm, cut to cut, friend to friend, to become blood brothers. They knew there was something binding in a blood covenant. Many tribal people had this custom as adults when they wanted to enter into a blood covenant with a friend. This covenant was binding for life. Those who were true to this covenant would die for one another. All their possessions became common property when this covenant was made. If the one who had made the covenant ever broke it at any time during his life, he was cursed, and cursed was the ground he walked upon. His own blood relatives would try to track him down and kill him for breaking it.
Some tribes had a custom of cutting the wrist of each person who wanted to enter into the covenant, dripping some of their blood into a glass of wine, and drinking it. They felt that it was a joining of each person's spirit and soul with the other, uniting them forever as true brothers. They sensed that the life was in the blood, so a joining of blood was a joining of life.
In the same way, the New Covenant, based on Yahshua's sacrifice, is a blood covenant. The Lamb of God shed His blood to bring us into His eternal life, His inheritance, His kingdom. He put everything He had at our disposal. He lived His whole life on earth, died and rose again for our sake, as it says in 2 Corinthians 5:15:
He died for all, that they who live should no longer live for themselves, but for Him who died and rose again on their behalf.
The response He requires, described in this passage, is a blood-covenant response. Those who truly enter His Covenant and are cleansed by His blood live their lives totally for Him. They express this devotion by placing their lives at the disposal of their brothers in the Covenant, without reserve. Any other response would be treating the blood of God's Son as unclean (Hebrews 10:29).