Sometimes Christians lose sight of the fact that the sacrificial aspect of the Jewish faith was central and paramount. As Christ came to bring the New Covenant, the blood sacrifices of the Temple yielded a higher and better order of sacrifice. We have in Holy Mass the presenting again of Christ’s sacrifice on the cross. But we are also called to make sacrifices. To sacrifice means to offer something to God. Because He is the God of the universe and Lord of all creation, He is rightly due whatever the very best is we can bring to Him. Not because He needs anything, but because we do.
In offering something of importance to God, whether a very valuable unit of livestock in the Old Covenant or the very shirt off our back in the New Covenant, we demonstrate proper moral rectitude. We humbly recognize our place in the order of creation. We acknowledge our absolute dependence upon God by showing Him that we can give up that which might otherwise be most dear to us. Sacrifice is giving away, believing that God will provide for whatever we think might be lacking in the giving.
To love God and our neighbor means to ultimately give ourselves away. It means to spend our mental and physical energy in pursuits that show the glory of God and make His graces evident to our fellow man. Loving God is not just a good feeling. Because we are so frail and fallible, our feelings change more often than the weather. Rather, to love God with our entire self is to give our entire self to Him. Clay in the hands of the Potter. He will then mold us into vessels that carry His grace to others who need it. This is how the entirety of the Law and Prophets can be so concisely summarized.