According to 1 Peter 3, Jesus, “proclaimed to the spirits in prison, because they formerly did not obey, when God’s patience waited in the days of Noah, while the ark was being prepared” (1 Peter 3:19-20). This is a rather strange passage, but it almost certainly doesn’t mean that Jesus was preaching the gospel to unbelievers who had died. The word spirits, when used without any qualifications (such as “spirit of man,” etc.) refers to supernatural beings, whether good or bad (Matthew 12:45; Luke 10:20; Hebrews 1:14).
Peter also says that these spirits were disobedient “in the days of Noah.” This probably refers to another strange passage in Genesis 6:1-4, where evil angels apparently had sexual relations with women and were “imprisoned” by God for it (see 2 Peter 2:4; Jude 6). This raises many other questions, I’m sure. In any case, it seems that here in 1 Peter 3, Jesus went to that angelic prison and proclaimed victory in light of the cross over these disobedient demons (see Colossians 2:15).
So Jesus did not preach the gospel to unbelievers in hell, at least not in an evangelistic sense.
-Francis Chan, Erasing Hell
Here are other Frequently Asked Questions and how the Bible answers them.