Matthew 9:13 (ESV) … “Go and learn what this means: ‘I desire mercy, and not sacrifice.’ For I came not to call the righteous, but sinners.”
When he became aware of the question: Matthew 9:11 ... “And when the Pharisees saw this, they said to his disciples, “Why does your teacher eat with tax collectors and sinners?”; Jesus rose to confront the hypocrites and their self-righteousness with righteous indignation. Jesus portrayed himself here, in the context of so many healing miracles, as a doctor for the human spirit. He defended his lack of association with the Pharisees (the healthy) by alluding to the fact that they saw no need for spiritual healing in themselves. He was not implying that the Pharisees were righteous, but only that they saw themselves that way, and so were not open to receiving his healing (forgiveness). It is safe to read some irony into Jesus’ use of the word healthy in referring to the Pharisees.
Jesus also defended his association with the tax collectors and sinners by their own self-awareness regarding their spiritual illness (sin) and their hunger for his healing (forgiveness).
Also implied in Jesus’ words was an affirmation of the basic equality of all people, a truth the Pharisees failed to grasp. This basic lack of understanding is why they needed to go and learn the lesson of Hosea 6:6. This Old Testament passage does not belittle sacrifice, but it elevates right treatment of the poor above it. By quoting the Old Testament, which the Pharisees knew well, Jesus shamed his opponents by confronting their misunderstanding of the spirit of the Lord’s Word. The word sacrifice here represents all the religious motions and rituals the Pharisees observed that were meaningless and empty. But accompanied by a heart after God, particularly a heart of mercy and compassion, righteous deeds take on positive significance before God (Matt. 6:1–18).
Compassion or mercy is an attitude toward a need that is compelled to take action to meet that need. A compassionate and merciful heart finds it impossible to remain neutral when it sees a need of any kind.
Jesus was not blind to the faults of the sinners with whom he dined, but his mercy caused him to withhold judgment. The Pharisees had no right to exercise judgment, since they were just as sinful themselves. They should have been the first to withhold judgment and accept the other sinners. But it in their pride, they were unmerciful, demonstrating they had no grasp of Jesus’ statements in 6:14–15.
Finally, Jesus clarified his “physician” analogy by saying, for I have not come to call the righteous, but sinners. Again, we can read some sarcasm and irony into his use of the word righteous when referring to the Pharisees. They were not truly righteous, but they saw themselves as such. Thus they were not willing to accept his forgiveness and respond to his call. The sinners, on the other hand, were aware of their sin (Matt. 5:3, “poor in spirit”) and hungered for forgiveness. They responded to his call to true discipleship. Jesus’ disciples were not perfect, but they accepted his forgiveness with humility and moved on toward maturity.