At the opening of the service, a call to worship has oriented our thoughts and affections towards God, and we have responded in song. Having praised God for who he is—holy, sovereign, faithful, loving—we realize how unworthy we are to be in his presence. We then move from the praise cycle of the gospel pattern into the renewal cycle (see the "Why Liturgy?" post for more on gospel pattern).
Applying the Gospel
The renewal cycle emphasizes that we, as redeemed sinners, are only able to be in God's presence by his grace. This recognition can come through a particular prayer offered by a leader, a song, or by a confession of sin. As a liturgical element of the Sunday service, a regular confession of sin is an important application of the gospel itself.
Scripture teaches us that we should confess our sin to God (1 John 1:9; Proverbs 28:13; Psalm 32:5) yet also to one another (James 5:16). There are also examples of corporate confessions of sin (Daniel 9; Ezra 9). And Jesus himself tells us to confess our sins together in the Lord's Prayer: "Forgive us our trespasses." A corporate confession of sin with the body of Christ is a way to obey these commands and a means to foster humility before a holy and gracious God.
In secular culture, "sin" is no longer a category for our behavior or attitudes. And there is a tendency within Christian churches to emphasize God's grace while minimizing repentance because of a fear of sounding legalistic. In this context, a corporate confession of sin is an important and counter-cultural gospel practice.
What a Confession of Sin Doesn't Do
But we should understand what we are doing when we confess together. Christians who have already received forgiveness in Christ should never be under the impression that it is our confessions which cleanse us—only the blood of Christ can do that. But when done in faith and repentance, and confessions is a means of grace reminding of our forgiveness in Christ. Reading a confession of sin without faith in Christ does not make you right with God!
John Frame helpfully explains that "great fact governing the worship experience from beginning to end is that Christ’s work is complete, that he is raised from the dead. ... But worshipers should not be led to suppose ... that the work of redemption needs to be done over and over again."
Another hesitancy toward written confessions of sin is that they may be too formal and depressing. But they certainly don't need to be so. Confessions need not feel like they are "bringing us down" from the joy of worship and love of God. The opposite is the case. They amplify the meaning of grace and joy which flows our of being forgiven and reconciled! Jesus said that "he who is forgiven little, loves little" (Luke 7:47).
This why, after we have confessed, we include some kind of "assurance of pardon," often words of Scripture or a prayer which emphasize that all of our sins have been forgiven.
It's then with a deeper joy we sing songs and hymns like this: