The final verse in 1 Peter 4 sums up the section, but it also summarizes the central theme of the entire letter. You can see it for yourself in 1 Peter 4:19.
Peter’s primary theme throughout this letter has been the concept of suffering, and how the Christian should respond to it, and continue to serve Christ in spite of it. That is nothing surprising, because all believers will suffer, or have suffered, because of their faith in God. What is surprising here is that Peter indicates that this is God’s will.
This is not the first time he has alluded to this idea. In chapter 3, Peter gave us another glimpse that the reality of suffering is something that God can and will use for his glory and for our own growth.
At first glance, we are tempted to think that unjust suffering is not what God would want for our lives, and that unjust suffering is caused by the enemy. To a certain extent this is very true. But as we see in the book of Job, along with other passages of Scripture, God is in control of each and every situation, and he ultimately controls all of humanity, and even the enemy and his demons. In that regard, everything he allows to happen is within the span of his will.