It seems to me the difference between these two groups is that the tax collectors and sinners are somewhat conscious of their sins and, hence, of their need to repent, but the scribes and Pharisees see themselves as righteous, as spiritually well, thus needing no physician to heal them. A more subtle element comes into play here, too. Christ came into the world to heal, not to judge, to call us to repentance and blaze the path of righteousness. Insofar as our good works are motivated by legalism, by a self-congratulating sense of keeping the rules, they have the effect of keeping us from God and separating us from others by causing us to think we are somehow better because we try harder. In the case of fasting and abstinence, say, we have to see what are doing as a means and not as an end in itself. The end to which such efforts are a means is holiness, Christ-like-ness.Genuine righteousness comes through faith and is manifested by wholesome works. Like the teachers of the Law, very often we want to expel evil, to cast it out, to avert our gaze. Christ Jesus comes to transform evil, to stare it in the face, and to overcome it. When contemplating evil, I need look no further than my own heart. In the prayer at end of Lauds this morning (Tuesday, Week I of the Psalter), we pray: "The light of heaven's love has restored us to life; free us from the desires that belong to darkness."
As an observant Jew, but one who is Messiah and Lord, Jesus did not become unclean by contact with tax collectors, sinners, or even Gentiles. His touch makes the unclean clean. Can anyone imagine that the tax collectors and sinners who dined with Jesus walked away from this event unchanged? Of course, the textbook answer is "No! They would have been changed, their lives redirected!" More realistically, in our heart of hearts, which draws from our own experience, we can imagine them walking away unchanged. We can imagine this because of how often we walk away from Mass having received the Eucharist unchanged, that is, unrepentant. As we approach Advent perhaps we should give some thought to the reason for our hardness of heart. I urge you to consider this reason: maybe too often we receive communion not being properly disposed, that is, to use the old formulation, not in a state of grace, put more simply still, not having gone to confession for far too long.
If you think living the moral teachings of the church is difficult, you are correct. I would say that living this way, in the manner of disciples of Jesus, doing the right things for the right reason in the right way, is impossible on our own, even assuming that we really want to. We need the support of others who are committed to holiness, but more than that even, we need God's grace. Where and how do we receive the grace necessary to live as followers of Jesus? The answer is that we receive the grace necessary to be made whole, to be made healthy, to be made clean, through the sacraments. Post-baptismally, we receive the grace we need primarily in and through the sacraments of penance and Eucharist. To fully receive the grace the Eucharist holds for us, we must clear out all that blocks God's grace. Sin does not prevent God from communicating divine life to us, but it prevents us from receiving God's life and communicating God's love to others. So, like the scribes and Pharisees, we deny that we need a physician by not going to confession. By refusing to go to confession, we do not seek treatment for what ails us: sin. Like any untreated serious illness, sin results in death. Jesus is the healer of my soul.