How do we know that the church is made up of believers and sinners?

The church operates as a community of sinners saved by grace, highlighted in Paul's letters to the Corinthians. Each believer is sanctified and called a saint, yet they still contend with their sinful nature. Paul addressed significant sin and division within the Corinthian church but affirmed their identity as God's sanctified people. The reality is that every true church is made up of imperfect individuals who are continually being transformed by the grace of God. This understanding reinforces the biblical truth that where there is genuine salvation, there will also be a visible change in the believer's life, although not without ongoing struggle.