We absolve people from their sins for no other reason than for our parishioners to believe what is being proclaimed from the pulpit. Accordingly, none of them can say, “How can the pastor know the condition of my heart? What good is Absolution if I do not repent?” Answer: “Indeed, in this particular case there is no benefit. But there is a benefit when you believe in your Absolution. But this is certain: you are absolved. And for this reason your eternal punishment would be all the more dreadful if you did not believe the Absolution that God Himself announced to all sinners and that He ordered His pastors to continue to announce to them.”
This applies to the Sacraments as well. The water in Baptism saves us. When the Lord offers communicants the blessed brea and says, “This is My body, which is given for you,” it is plain that He means to tell them that they must believe or His body would not benefit them. A person who believes that Christ, by sacrificing HIs body, has paid for the communicant’s sins can leave the altar rejoicing and exulting. When the Lord offers the blessed cup and says, “This is My blood, which is shed for you for the forgiveness of sins,” He emphasizes the words “for the forgiveness of sins.” This causes every communicant who believes these words to shout with joy when he goes home from church after Communion.
Law & Gospel: How to Read and Apply the Bible by C. F. W. Walther (A Reader’s Edition)