For those who love God, the written law is unnecessary, not because it is not binding, but because one obeys out of love and not because of the external law. When one becomes free from sin, through Christ, one is discharged from the outside law because the natural law becomes informed by grace.
Law becomes internalized through love. One wants only to please God and not men. Yesterday, we heard in the Scriptures that God said David was a man "after His Own Heart".
David loved God, and God loved David. The relationship between David and God prefigures our own relationship with Christ, through the Church, the sacraments, and especially the Eucharist. Today, we see a prefiguring of that symbol in the fact that the priest in today's reading gives David the temple bread for his hungry soldiers.
Then, the high priest present to David his old sword, kept for posterity, used to cut off the head of Goliath years ago. David represents the Church Militant. Prayer first, action second.
David represents one of the patriachs whose lives reveal the plan of God in the world, preparing the world for Christ. This is our job as well, to bring Christ into the world through prayer and evangelization. But, nothing can be done without purity of heart, the theme of today's readings.
1 Samuel 21:2-10,22:1-5