In the synagogue a man with a withered hand is present, and some watch to see whether Jesus will heal him on the Sabbath so they can accuse him. Jesus asks whether it is lawful on the Sabbath to do good or to do harm, to save a life or to kill, and no one answers. Angry and grieved at their hard hearts, he tells the man to stretch out his hand, and it is restored. The Pharisees go out and immediately plot with the Herodians how to destroy him.
Jesus withdraws to the sea with his disciples, and a great crowd from Galilee, Judea, Jerusalem, Idumea, beyond the Jordan and around Tyre and Sidon follows him. Unclean spirits fall down and call him the Son of God, but Jesus orders them not to make him known. Then he goes up a mountain and calls those he wants: he appoints twelve to be with him, to be sent out to preach and to have authority to cast out demons. Mark gives the list, including Simon, whom he names Peter, James and John, whom he calls Boanerges, sons of thunder, and Judas Iscariot, who betrayed him.
Back at a house, the crowd is so large that they cannot even eat. His relatives set out to take charge of him, saying he is out of his mind. The scribes from Jerusalem accuse him of casting out demons by Beelzebul, the prince of demons. Jesus replies that a kingdom or house divided against itself cannot stand, that no one plunders the strong man's house without first binding him, and that whoever blasphemes against the Holy Spirit has no forgiveness. When his mother and brothers arrive and send for him, Jesus looks at those sitting around him and says that whoever does the will of God is his brother, sister and mother.