We love the stories about Martha and Mary, so pardon me for turning to the first reading. At the consecration of the Mass we call the blood the blood of the new covenant, and to get the full import of that, we should read the story about the blood of the Old Covenant.
First, we should grasp the importance of covenants. We all sign contracts by which we exchange sums of money for cars or apartments or other things of value. Well, a covenant is also a contract, but it differs from other contracts in that what we exchange is our very selves.
For the marriage contract the priest asks the man and woman, “Have you come here freely to give yourselves to each other in marriage.” For the Old Covenant God said, “You will be my people, and I will be your God.”
For parties to belong to each other, they must agree to accept each other as they are. For marriage we promise to love and cherish. For a covenant with God, who cannot stoop to our level, we must rise to his level. So, Moses asked the people if they would obey each of God’s commandments.
The people of the Old Covenant saw blood as vital as we see the breath of life. By exchanging blood, they felt they were entering into to an identity sharing union with each other.