After Jesus’ first meeting with the leaders of Judaism since the beginning of his public ministry, Luke continued to record their response to him and his claim to be the Messiah. They seem to be very attentive of Jesus’ activity, challenging his disciples about his and their willingness to keep company with publicans and sinners. When Jesus saw what was occurring and spoke for his disciples, the doctors of the Law confronted him about his public religious spirit (i.e. fasting). Yet, at each turn Jesus responded in such a manner that exposed the apparent self-righteousness of the scribes and Pharisees, showing how they overlooked the weightier matters of the Law, while they made a public show of their own personal religious prowess.
As I claimed in a previous study, Levi is Matthew, the apostle of Jesus and writer of the Gospel of Matthew. In all four lists of the apostles Matthew is mentioned, not Levi. Both Luke and Mark use the name Levi when they show he is a tax collector, whom Jesus calls (Mark 2:14; Luke 5:27). Matthew alone records the incident under the name Matthew (Matthew 9:9) and admits to being a publican (Matthew 10:3).
I think Levi knew Jesus prior to his calling, but not necessarily before Jesus’ baptism. Since he was a collector of taxes at Capernaum (Matthew 9:1, 9; Mark 2:1, 13-14), he may have known Jesus as one who paid his taxes to Herod, but there seems no context for their being friends. Nevertheless, Levi / Matthew may very well have heard of Jesus, the miracle worker who recently began his public ministry. In any event Levi made what Luke terms a great feast in Jesus’ honor and invited many of his friends, all of whom the religious leaders viewed as sinners. Needless to say, the event provoked questions from the doctors of the Law and the Pharisees.
They first approached Jesus’ disciples, asking why Jesus and they ate with publicans (tax-collectors) and sinners (Luke 5:30). Whether or not the disciples tried to answer is not recorded, but the text does say it was Jesus who replied (Luke 5:31). Both Matthew and Mark add “when he (Jesus) heard it…” implying one of the disciples may have gone to him about the question, or one of the quests told Jesus what was happening, or Jesus, himself, either heard the question or saw that the Pharisees and lawyers were speaking with the disciples. Whatever the reason, all texts agree that Jesus was the one who replied to the doctors of the Law and the Pharisees. Jesus claimed that those who are already righteous don’t need a physician. Rather, it is those who are sick who are in need (cf. Jeremiah 8:22).
Jesus’ reply (Luke 5:31) invoked the Jewish leaders’ own doctrine that sin is a disease (cf. Luke 5:20-23). The man stricken with palsy was miraculously healed and so immediately that even atrophy was healed and accounted as part of the miracle. Jesus’ remark in Luke 5:31 appeals to his analogy in Luke 5:23. However, unlike the immediacy and totality of the miracle with the man stricken with palsy, Jesus shows the sinners, or the spiritually diseased, need care in order to make their healing complete. Just as the man stricken with palsy would have needed exercise had Jesus not healed his atrophy as well as his body in the miracle mentioned in Luke 5:20-25.
Repentance brings God’s healing, but ordinarily, there is much work to be done in the process of complete healing (cf. Philippians 2:12). There will be tests and failures, facing problems and successes along the way, but the Great Physician has promised to be with us with healing in his wings (Malachi 4:2).
Jesus told the Pharisees that he had not come (as a physician) to call the righteous to repent (i.e. to cure the healthy), but, rather, he is come to call the unrighteous to repent (to cure the those who are spiritually ill (Luke 5:32). The Pharisees and the scribes (doctors of the Law) had considered themselves righteous, not in need of repentance. Therefore, they had no need of Jesus’ power to heal them. So, Jesus’ remark was a rebuke, meant to cause them to look more deeply at themselves.
 Matthew 10:2-4; Mark 3:14-19; Luke 6:13-16; Acts 1:13, 26.