It is important to keep the context in mind when considering a passage such as this. In verse 4 Peter refers to unbelievers who persecute believers. They will give an account to God (v. 5). Their condemnation of believers will itself be judged by God. It is important to remember that that the overall argument of First Peter is to vindicate those who suffer for preaching the gospel.
The argument of First Peter is that believers should endure persecution from unbelievers knowing that they have eternal life before them. The argument then is that believers should persevere with the criticism by the lost because God will judge their critics (v. 5). It does not follow that Peter should change his argument to a promise of a second chance. A second chance rips the heart out of the entire argument of a book that shows Christians how to suffer for Christ.
Verse 5 points to the accountability of unbelievers to God but verse 6 shows that believers will possess eternal life—“live according to God in the spirit.” The censure of unbelievers is “according to men” but believers will ‘live according to God.” The final judgment is not in view in v.6 as it was in v.5.
The “for” in verse 6 explains verse 5. Verse 6 draws attention to those who had previously believed but are now physically dead at the writing of First Peter. Verse 6 is a particularization of those who died. The phrase “to those who are dead” (tois nekrois) is literally “those dead ones.” There is no verb, so the translation would be “was preached also to the dead ones.” There is no “are preached” as if there is a current preaching ongoing to dead people. The thrust then is that the gospel was previously preached at a previous point to those who are now physically dead.
The aorist passive indicative of “was preached” indicates that the preaching occurred at one point in the past. The “also” in this case would be a different classification than those in verse 5. The point here is that these people believed the gospel when they were alive and subsequently died.
Unbelievers viewed their death as proof that there is no advantage of becoming a believer because everyone without exception dies. To contradict this thinking Peter argued that unbelievers do not get the entire picture when making this claim. Death is not the last word for believers because God will raise them from the dead. The words “live in the spirit” refer to eternal life. We can see this contrast between “flesh” and “spirit” in 3:18 where Christ died in His flesh but was raised to life by the Holy Spirit. Believers have a similar destiny; they die physically but will be raised to eternal life by the Holy Spirit. Peter’s use of the present tense and subjunctive mood “live according to the spirit” shows the certainty of this coming to pass. It is assurance of their eternal future that lies ahead.
It is important to note that in 1 Peter 3:19 the “spirits” are not human beings. The gospel was not preached to human beings after their physical death. Thus, 4:6 is not an elaboration of 3:19. Also, 3:19 does not refer to preaching the gospel whatsoever but to a “proclamation” of triumph over demonic spirits (see my study on that verse). The word “preached” in 3:19 is different from the word in 4:6 (euaggelizo), the word translated “preached” there is kerysso. That word was used in secular Greek of an official announcement or proclamation made by a representative of a government. The word in itself does not indicate the content of the message. A qualifying phrase must be used for that purpose. In the New Testament, the word kerysso is used either with a qualifying phrase such as “the gospel” (Mark 16:15), or the contents of the proclamation are given as in Revelation 5:2, or it is used alone without the contents of the message being given as in Romans 10:15. Thus, one cannot say that our Lord preached the gospel to these fallen angels. There is a distinct word used in the Greek New Testament which means “to preach the gospel,” euaggelizomai. In Luke 4:18 we have, “to preach the gospel to the poor,” where the words, “preach the gospel” are the translation of the one word euaggelizomai. The word is made up of aggello “to bring a message,” and eu “well” or “good,” thus, “a message of good,” thus, “to bring good news.” The word “gospel” means “good news.” But this word is not used here. Our Lord made an official proclamation to these fallen angels. It was not the gospel.
As well, the verb in “the gospel was preached” (euēngelisthē) in 4:6 is in the passive mood, thus the gospel preached does not refer to the preaching done by Christ but to the preaching of Christ. The preaching was done by human preachers, not by Christ.
There is no textual evidence for Christ preaching the gospel after a person has died. Neither is there any evidence in the text for limiting the dead to those who lived before the incarnation (OT saints) or for those who have not had an opportunity to hear the gospel. The NT nowhere else suggests that a person can become a believer after death or that all dead will be saved (cf. He 9:17).