What does 1 Peter 3:18 mean?

Peter has just stated that Christians are sometimes called to suffer, by the will of God, for doing good. Here, he again reminds his readers that's exactly what Jesus Himself did for us. This is a concise summary of what exactly happened when Jesus died on the cross.

First, He suffered, which is quite an understatement in the context of Roman crucifixion. Next, His suffering was for sin—not His own, but ours. And, importantly, Christ suffered and died only once. Jesus was the sacrifice for sins but, unlike the annual animal sacrifice for sins in Old Testament, Jesus was the final sacrifice for sin. God required no more blood, no more death.

Then Peter reveals that Jesus' sacrificial death was as a substitute—the righteous (Christ) for the unrighteous (us). Why did He do it? To bring us to God. Without Jesus' death for our sins on the cross, we could not come to God. Because of it, all who trust in Christ are brought to His Father. What was the result? Physical death, but not permanent death.

Following His crucifixion, Jesus was "made alive in the spirit." Bible scholars offer multiple explanations for what this phrase might mean, especially in light of the following verses. The most obvious explanation is that Jesus was resurrected from the dead by the Holy Spirit, something clearly taught in the rest of Scripture. Another explanation is that while Jesus was physically dead, His own personal spirit—Himself in Spirit form—somehow was made alive before His physical resurrection to accomplish what is described in the following verses.