What does Matthew 12:3 mean?
Some Pharisees have seen Jesus' disciples picking off heads of grain and eating them while walking through a field on the Sabbath (Matthew 12:1–2). The Pharisees have complained to Jesus that what the disciples were doing was unlawful. The fourth of the Ten Commandment forbids working on the Sabbath (Exodus 20:8–11). According to the Pharisees' traditional interpretation of that command, picking the heads off the grain qualified as harvesting or reaping: a form of "work."Jesus will firmly reject their accusation and their interpretation of the Law, using Scripture to back up His reasoning. He starts by asking if they have not read what David and his friends did when they were hungry (1 Samuel 21:1–6). Of course, Jesus knows that the Pharisees have read that story. These men had read Scripture in its entirety. His point is to hold them accountable for not applying the Scripture according to the actual intent of God. The Pharisees are applying the law as hypocrites, failing to notice the real lives of those under their spiritual care.
Jesus continues His question about that moment in David's life in the following verse.