Christ teaches this and later commands that from that point on—to the end of the world—the Church should observe that repentance and forgiveness of sins are to be preached. Let everyone, then, learn that he must seek forgiveness of sins from fellow human beings and from nowhere else. For thus reads the command of our Lord Christ: “Truly, I say to you … whatever you loose on earth shall be loosed in heaven” (Matthew 18:18). Likewise, “If you forgive the sins of anyone, they are forgiven” (John 20:23). For God will not tolerate the building of special ladders and stairways to heaven to suit every individual. He alone wants to be the sole Architect.
Accordingly, if you desire your sins to be forgiven, go and be baptized, if you are still unbaptized. Or if you have been baptized, remember the promise that God made at your Baptism and do not be unbelieving. Likewise, go and be reconciled to your neighbor, and then ask for Absolution. And when you hear the announcement of the forgiveness of your sins in the name of Jesus, believe it, and truly you will have it. After that go to the most venerable Sacrament and receive the body and blood of Christ in the assurance that this precious treasure is meant for you and that you may enjoy it as your own, etc.
Baptism, Absolution, preaching, and the Sacrament are not to be despised, but in them forgiveness of sin is to be sought and obtained. To this end, God has called and commissioned your pastor, your father and mother, and your closest fellow Christians and has put His Word in their mouth, that you are to seek consolation and forgiveness of sin from them. For though human beings are talking to you, still what they say is not their own [word] but God’s Word. Therefore, you should believe it firmly and not despise it. …
This is why Anabaptists and other sects have lost in one stroke the forgiveness of sins, Baptism, the Sacrament, the Christian Church, and all Christian works: because they reject the Word when they hear it from their fellow man, regarding it as nothing better than the bleating of a calf. Well, suppose God were to speak to you through some cow or other animal, as He once spoke through a donkey?97 … Still, you are not to despise His Word, but regard it as valid. Why, then, would you despise it when men speak it by the command and order of God? For though you indeed hear a man’s voice, you do not hear a man’s [word] but God’s Word, and you surely will receive the forgiveness of sins attached to it, if you will only accept it by faith.
"Law and Gospel: How to Read and Apply the Bible"