In Philippians 3, Paul's prescription for church unity is to rejoice in the Lord. Rejoicing in the Lord means finding our joy, our security and our status in what Jesus has done for us rather than in what we've done for Jesus. When we all share equallyin God's grace, we all stand on level ground, but if our status is based on our accomplishments for God, believers will compete with each other in ways that make unity impossible.
