Jesus answered the Pharisees from their own Scriptures. "Have ye never read" was a pointed question to men who knew the Law well: of course they had read it, but they had missed what it meant for this case. He pointed them to David in a moment of need, when he and his men were hungry (1 Samuel 21:1-6). Barnes explains the principle Jesus drew from the story: "In cases of necessity the laws did not bind a man," "a principle which all laws admit" (on Matthew 12:3). Gill applies it to the disciples: since David ate when hungry, "it ought not to be charged as an evil upon the disciples, for plucking and rubbing a few ears of corn to satisfy their hunger."

Jesus finished the story Himself: David "went into the house of God in the days of Abiathar the high priest, and did eat the shewbread, which is not lawful to eat but for the priests" (Mark 2:26). Then He drew the lesson: "The sabbath was made for man, and not man for the sabbath: Therefore the Son of man is Lord also of the sabbath" (Mark 2:27-28). Mark records no answer from the Pharisees. Later, on a sabbath in the synagogue, they "watched him... that they might accuse him" (Mark 3:1-2).

The story comes from 1 Samuel 21:1-6. David, "fleeing before Saul" as Barnes puts it (on Matthew 12:3), came to Nob and asked Ahimelech the priest for bread. The priest had "no common bread," only "hallowed bread," the shewbread "taken from before the LORD," and he gave it to David (1 Samuel 21:4, 6).

Only Mark includes the words "when he had need." Matthew and Luke say simply that David "was an hungred" (Matthew 12:3; Luke 6:3). Mark's added phrase puts the weight on David's need, which matches the disciples' situation.

Jesus treated Scripture as the place to settle the question, and He read it with mercy in view. The Pharisees knew David's story but used the Law to condemn the disciples, who Matthew says were hungry (Matthew 12:1). Jesus used the same Scriptures to show that God's law was never meant to be turned against human need. In Matthew's account He adds, "if ye had known what this meaneth, I will have mercy, and not sacrifice, ye would not have condemned the guiltless" (Matthew 12:7).

Matthew Henry, voicing Jesus' point, writes that "David, the man after God's own heart, when he was hungry, made no difficulty of eating the show-bread, which by the law none might eat of but the priests." Jesus' point was not that David was above the law, but that God's own Word had not condemned him.