There are several compelling reasons that Christians must grow spiritually. First, it glorifies God. Second, it provides evidence that their salvation is genuine. Third, it adorns and makes visible the truth of God to others. Fourth, it brings assurance of salvation. Fifth, it preserves believers from the sorrow and suffering associated with spiritual immaturity. Sixth, it protects the cause of Christ from reproach. Seventh, it produces joy in believers’ lives. Eighth, it equips them for ministry to others in the body of Christ. Finally, it enhances their witness to the lost world.
John MacArthur