There are two ways to approach God. One is safe, and the other leads to death. Since the Fall, to approach God uncovered, that is, without blood, is to die. Think of Adam and Eve in the Garden. After they sinned, they tried to make coverings for themselves with fig leaves. But there was no blood. God covered their sin and shame by the first shedding of blood. He killed an animal and turned its skin into clothing.
Today Our Lord tells us a Parable about righteousness and how it is achieved. There are two ways, one of life and one of death. If your righteousness is internal, if it is self-focused, it is not true righteousness. On the other hand, if your righteousness comes from outside of you, if it is counted to you apart from your deeds, then it is true righteousness. Jesus tells us that the tax collector, though perceived as unrighteous, went to his house justified, while the Pharisee, regarded as extremely righteous, goes home condemned. True righteousness only comes when one is covered by the greatest Sacrifice, Christ Jesus.
Why does the Pastor preach? Scripture explains that the role of preaching the Word of God is how saving faith is created: “How then will they call on Him in whom they have not believed? And how are they to believe in Him of whom they have never heard? And how are they to hear without someone preaching? And how are they to preach unless they are sent? As it is written, ‘How beautiful are the feet of those who preach the good news!’ … So faith comes from hearing, and hearing through the Word of Christ” (Romans 10:14-17). The Augsburg Confession, seeing this connection between the Preaching Office and saving faith, summarizes Scripture on the Office of the Holy Ministry in this way: “To obtain [saving, justifying] faith, God instituted the Office of Preaching, giving the Gospel and the Sacraments. Through these, as through means, He gives the Holy Spirit who produces faith, where and when He wills, in those who hear the Gospel. It teaches that we have a gracious God, not through our merit but through Christ’s merit, when we so believe” (AC V 1-3). The whole reason the Pastor preaches is so saving faith can be created, so we know that “we have a gracious God” who loves us and has saved us from our sin by the death and resurrection of Jesus Christ.