How do we know that the gospel is essential for fellowship?

Fellowship among Christians is deeply rooted in a shared belief in the essential truths of the gospel. Romans 16:17-18 instructs believers to mark those who cause divisions contrary to the doctrine learned, indicating that if someone preaches a false gospel, they are not part of the fellowship. The true gospel, grounded in God's free and sovereign grace, establishes the doctrinal foundation that unites believers. All who are in the faith share a common understanding of sin, Christ's atonement, and the righteousness that is imputed through faith alone, thus making it vital that fellowship is maintained with those who uphold this truth.