Book excerpt: When Paul heard that a Christ-follower in Corinth was in an incestuous relationship with his stepmother, the apostle insisted the man be removed immediately from the congregation. This dramatic response is surprising, as Paul responds to other serious situations with much less vehemence. Why did Paul react to the immoral man with such urgency and severity? Using socio-cultural tools, this study explains the importance of group identity and witness for Paul’s ecclesiology. The argument lays a foundation for contemporary readers to appraise contexts where an expulsive response to sin might be appropriate.