To encourage believers to endure suffering for righteousness’ sake, on account of their faith in Christ, in chapter 3:18-22 of his first letter, Peter gives us a most beautiful description of the redemptive work of Christ on our behalf as a motivation.
Peter here is showing that not only was sin defeated through Christ’s suffering and death, but Satan was also defeated; and in their suffering, the believers also could know victory over Satan through faith in Christ (Rev. 12:11). Even if they were to lay down their lives for Christ, it would not be in vain. Through their testimony, others would come to faith and Christ would build His church.