In I Peter 4, the apostle returns to the subject of preparing us for life in this fallen world. This issue was a great burden on the heart of the apostle and that is reflected in the amount of time and ink he devotes to it. But even though he returns to this topic, the nature of his instruction to us has changed. Before, he instructed us to patiently bear up under various persecutions. His focus now is more on the conflict and how we ought to arm ourselves for it.
The first preparation which the apostle provides is the exhortation to arm yourself with the "mind of Christ". All through this long discourse the apostle has pointed to Christ and said, do as He did; behave as He behaved; bear up as He bore up under the unjust persecutions He endured. He has walked the steps you walk in and He has experienced the trials you experience. Therefore, arm yourself with His way of thinking and perceiving. That is, he would have you have the same confidence in the justice of the Father and the same wisdom which the Savior had. (I Cor. 2) But remember, if you strive in your own strength, you will fail. If you seek to know by your own wisdom, you will fall.
The second preparation is the exhortation to arm yourself for the fight against sin. When we are in Christ by faith, this means more than just the forgiveness of sins. It means that we have a unity with Christ in His death and resurrection. (Romans 6) Christ conquered sin and death; in Him, we are conquerors of sin and death – at least in principle. Since you are in Christ and identify with Him in death, your life ought to reflect that conquest of sin and death. To reinforce his point, Peter reminds us that the sinful life and lusts we pursued apart from Christ were enough. We do not need to add to those sins now; they were sufficient.
The third preparation which the apostle provides is the exhortation to anticipate the trials of standing for righteousness. If you are armed with the mind of Christ and you live it in the world, you are going to have to be ready to stand for uprightness and for the opposition it will generate. Peter informs you that the world will be surprised and confused by your stand. This should not surprise us. He also tells you that the world will speak evil of you. This also should not surprise us. The world cries, "live and let live." Yet, in practice that is not what happens, nor can happen. Simply living the Christian life is a testimony against the darkness and those in it. You don't have to try – it just is. When you are confronted with this, "Remember the word that I said unto you, The servant is not greater than his lord. If they have persecuted me, they will also persecute you; if they have kept my saying, they will keep yours also." (John 15:20) That is, arm yourself with the mind of Christ.