At the Last Supper Jesus gave his disciples a new commandment: they were to love each other as he loved them.
It was no accident that Jesus chose that time to give them his commandment. The Last Supper was a covenant ceremony, and commandments are integral to covenants.
Think back to the elements of the covenant ceremony in Exodus, Chapter Twenty-Four. The Levites went about, sprinkling blood on each participant and on the altar that represented God. The Israelites believed blood to be life itself. By its falling on each of them and on God’s altar they were all made into one living entity with each other and God.
While the blood was being sprinkled Moses was asking the people to call out their acceptance of the commandments: “Will you honor your father and your mother?” “Will you keep holy the Sabbath?”
We have similar questions in the covenant ceremony we call marriage: “Will you love and honor each other for the rest of your lives?”
A covenant is an agreement by which two parties become one. To that end they must do away with whatever would push them apart. That is where the Ten Commandments fit into the Old Covenant. Loving others as Jesus loves us is an important part of the Covenant of the Mass. If you are not willing to love others as Jesus loved them you are not becoming one with them, and you are not taking part in the Mass.