What the Bible says about Suffering as a Requirement
(From Forerunner Commentary)
Peter's choice of words makes suffering a requirement! God called us to emulate Jesus Christ in doing good, and because of the anti-God bent of the world, some suffering is guaranteed to result from doing the right thing. It often offends our sense of justice to see the wicked prospering while the righteous endure hardship and grief. In the long term, God's justice will be served, but in the meantime, we may need to adjust our expectations for leading a comfortable or easy life. If we have been called by God, we must follow the example of Christ, which epitomized unjust suffering while always doing good.
David C. Grabbe
A Look at Christian Suffering (Part Three)