At that time, Jesus was going through a field of grain on the sabbath. His disciples were hungry and began to pick the heads of grain and eat them. When the Pharisees saw this, they said to Him, "See, Your disciples are doing what is unlawful to do on the Sabbath."
He said to them, "Have you not read what David did when he and his companions were hungry, how he went into the house of God and ate the bread of offering, which neither he nor his companions but only the priests could lawfully eat? Or have you not read in the law that on the sabbath the priests serving in the temple violate the sabbath and are innocent? I say to you, something greater than the temple is here. If you knew what this meant, 'I desire mercy, not sacrifice,' you would not have condemned these innocent men. For the Son of man is Lord of the sabbath."
What David did
The Torah of Moses forbids the Israelites to do work on the Sabbath, so they can rest and celebrate the Lord's work of creation (Ex 20:8-11) as well as the salvation He offered them when He freed them from the slavery of the Egyptians (Dt 5:12-15). In their zeal to safeguard the Sabbath rest, the rabbis have come up with a list of 39 kinds of work prohibited on the sabbath. …