“…In this Christian Church He daily and richly forgives all my sins and the sins of all believers…” (SC, The Third Article: Sanctification).
Just as the Holy Spirit has “called me by the Gospel, enlightened me with His gifts, sanctified and kept me in the truth faith,” so He accomplishes this work in the Christian Church. So, why go to church? As said in the previous post, church is not a social club. Church is the local, holy (set apart) means by which God has chosen to distribute His means of grace for the forgiveness of sins: in His Word and Sacraments.
“Can’t I just ask God for forgiveness on my bed?” Of course you can. But what do you do when your conscience becomes your worst enemy? What do you do when you don’t feel forgiven? What do you do when you believe the devil’s lies, “God didn’t actually forgive you”? Go to church—and if you can’t wait till Sunday, go to your pastor during the week—and receive His Word and Sacraments that physically deliver forgiveness to you. You don’t need to doubt because you heard it from your pastor as from Christ Himself in Confession & Absolution. You don’t need to doubt because you remember you were washed in Holy Baptism (see 1 Corinthians 6:11). You don’t need to doubt because you tasted and consumed Christ’s forgiveness in His true body and blood in the Lord’s Supper. As I preached on Reformation Day (Observed) last year, “The devil’s whispers may still linger afterward, but he cannot undo what God said in the Sacrament. The devil might even convince you, but God remains convinced that you are innocent, washed clean by the blood of the Lamb [Rev. 7:13-14].” As a Christian, you are part of the Body of Christ, and no Christian cuts themselves off from His body, lest you wither and die (1 Corinthians 12:12-27). Christians physically gather in a local assembly; it’s what they do.
I read something a pastor once said, “People have a more difficult time forgiving than God does. We seem to lay our burdens at the foot of the cross, only to pick them back up again as we leave” (Devotions on the Small Catechism, 59). When you walk away from the Supper Table, you don’t pick your sins back up again. Rather, you leave them there, dead. You might not feel forgiven, but forgiveness doesn’t depend on what you feel. Forgiveness depends on what Christ did for you on the cross and in His victory when He rose from the dead.
Various Authors. Devotions on the Small Catechism. Saint Louis: Concordia Publishing House, 2019.