What does Matthew 12:13 mean?

To trap Jesus, a group of Pharisees have asked whether it is lawful to heal on the Sabbath. The heart of the question is whether non-life-saving healing involves work. That would make it a violation of the letter of the fourth commandment (Exodus 20:8–10). Unless the person is in life-or-death need of help, the Pharisees say healing is unlawful.

Jesus has countered that it is lawful to do good on the Sabbath, providing an illustration of a sheep that falls into a pit. Who would not show mercy by bending to help that sheep out? His point is that while the literal words of the law have meaning, they also have intent—and God's intent was not to choose evil over good for the sake of legalism (James 4:17).

The man with the withered hand has not said or done anything. In a very real sense, this conversation is not about him. It involves him, but it's not even tied to his faith, the subject of so many of Jesus' miraculous healings. The sense of this scene is that everyone present believes Jesus can heal this man's hand whenever He wants to. Even the Pharisees seem to believe this, cynically hoping for a miracle so they can condemn the miracle-worker!

Jesus, though, has reframed their trap into a question of doing good or doing evil, of showing mercy or refusing to do so. Jesus now acts in mercy. He tells the man to stretch out his hand. When he does so, the man's hand is restored, as healthy as his other one. He has been healed on the Sabbath in the synagogue by the Messiah.