What is Confession? “Confession has two parts. First, that we confess our sins, and second, that we receive absolution, that is, forgiveness, from the pastor as from God Himself, not doubting, but firmly believing that by it our sins are forgiven before God in heaven” (Small Catechism).
Another way our Confessions put it is that confession (or repentance) has two parts: contrition and faith. Contrition “is the genuine terror of the conscience that feels God’s wrath against sin and grieves that it has sinned. This contrition takes place when the Word of God denounces sin” (Ap XII, 29). The second part is faith, “namely, that in the midst of these terrors, the Gospel about Christ (which freely promises the forgiveness of sins through Christ) ought to be set forth to the conscience. They should therefore believe that on account of Christ their sins are freely forgiven” (Ap XII, 35).
In contrition, then, which we can also call godly sorrow, the penitent confesses their sin to God. Then in faith, the penitent trusts in the promise of Christ’s Word that he or she is absolved from their sin. Confession, then, is the humblest thing a person can do, for who likes to admit they’re wrong? It is especially difficult to do this before one’s pastor, to whom Christ has given the authority to forgive you your sins in His stead and by His command. A later column will talk more about this. For now, it should suffice to quote from Luther:
Therefore, if you believe the word of the priest when he absolves you… then your sins are assuredly absolved before God, before all angels and all creatures—not for your sake, or for the priest’s sake, but for the sake of the very Word of Christ, who cannot be lying to you when He says, “Whatever you loose… shall be loosed” [Matthew 18:18]. …Besides, you had better not go to the priest if you will not believe his absolution; you will be doing yourself great harm by your disbelief. By such disbelief you make your God to be a liar when, through His priest, He says to you, “You are loosed from your sins,” and you retort, “I don’t believe it,” or, “I doubt it.” As if you were more certain in your opinion than God in His words, whereas you should be letting personal opinions go, and with unshakeable faith giving place to the Word of God spoken through the priest.
LW 35:13-14
Because of Christ’s command (see John 20:21-23), when your pastor forgives you your sins in public Confession & Absolution, you heard these words as from Christ Himself; therefore, you are forgiven. The same occurs when you confess your sins in private Confession & Absolution. We think this is only something Roman Catholic priests do, but we do it in the Lutheran Church as well. We don’t have little boxes in which we do them, but our office doors are always open for you to come through and confess the sin that is weighing on your conscience, and we will prescribe you with the efficacious elixir of the Gospel for the forgiveness of your sins in the Sacrament of Absolution, perhaps even the Lord’s Supper. And that is why this Sacrament is such an enormous comfort, because it is a means of grace God has given you through your pastor, who is to act as Christ before you, to grant you forgiveness of sins when your conscience becomes your worst enemy.
The Lutheran Column 