As he was passing through a field of grain on the sabbath, his disciples began to make a path while picking the heads of grain. At this the Pharisees said to him, “Look, why are they doing what is unlawful on the sabbath?” He said to them, “Have you never read what David did when he was in need and he and his companions were hungry? How he went into the house of God when Abiathar was high priest and ate the bread of offering that only the priests could lawfully eat, and shared it with his companions?” Then he said to them, “The sabbath was made for man, not man for the sabbath. That is why the Son of Man is lord even of the sabbath.”Mark 2:23-28
The sabbath was created for man destined for union with the uncreated God. Thus the sabbath serves man and not vice versa. Sabbath observance is not an end in itself. The source of shalom, God, is the end of humankind. This God has become man in Jesus Christ.
Taking on our human capacity to become hungry and thirsty, Jesus shows the utmost kindness and tenderness towards his brethren by relieving their hunger out of reverence for the Lord of mercies on the sabbath.
From the Catechism of the Catholic Church 2173:
The Gospel reports many incidents when Jesus was accused of violating the sabbath law. But Jesus never fails to respect the holiness of this day. He gives this law its authentic and authoritative interpretation: “The sabbath was made for man, not man for the sabbath.” With compassion, Christ declares the sabbath for doing good rather than harm, for saving life rather than killing. The sabbath is the day of the Lord of mercies and a day to honor God. “The Son of Man is lord even of the sabbath.”
The Lord of the Sabbath has become man.
For man was the Sabbath made in God’s plan.