Sometimes a Christian will be called upon to suffer undeservedly for thinking and behaving as a Christian. When he does it is God's will, vs. 17. When we go through these difficult times faithfully, we are nevermore like Christ, and never closer to Him. We are experiencing "the fellowship of His sufferings."
Furthermore, our suffering for righteousness' sake brings great benefit, not only to us, but also to other people. The PROOF that this is true, and the MOTIVE for rejoicing when we suffer for Christ is none other than the experience of undeserved suffering in the life of Jesus Christ Himself, the prince of sufferers. Believing meditation on the sufferings of Christ - their nature, purpose and consequences - will reconcile the Christian to undeserved persecution and slander, and will give him support and direction while being persecuted.