New Covenantعينة

The Bible does not say much about the terms of the new covenant, but it tells us some things, for example, in Mark's gospel we read, “One Sabbath Jesus was going through the grainfields, and as his disciples walked along, they began to pick some heads of grain.” The Pharisees said to him, “Look, why are they doing what is unlawful on the Sabbath?” He answered, “Have you never read what David did when he and his companions were hungry and in need? In the days of Abiathar the high priest, he entered the house of God and ate the consecrated bread, which is lawful only for priests to eat. And he also gave some to his companions.”

If the law commanded not to work on the Sabbath, why did Jesus defend his disciples when they harvested grain on the Sabbath and quote this passage where David also transgresses the law?