Theophylact of Bulgaria
The connection is this: these men who speak evil of you will give answer to Him Who judges all the living and the dead.
The dead also are judged. This is clear from the Lord's descent into Hades. For after His death on the Cross He appeared there and preached there also, as on earth. He preached not by word, but by deed.
His dwelling in the world served for justification to those who readily acknowledged Him, and for condemnation to those who did not acknowledge Him. So also among those held in Hades, He appeared for condemnation to those who lived according to the flesh.
But to those who lived according to the spirit, that is, who led a spiritual and virtuous life, He appeared for glory and salvation. Therefore He is rightly called Judge of the living and the dead.
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St. Cyril explains it otherwise. Here he calls "dead" those among the pagans who killed themselves by the sins named in 1 Pet 4:3. The apostle prays that they may be converted and render a blameless answer to Him Who is to judge the living and the dead.
He also calls the righteous and the sinful "living and dead." To them God the Word, appearing in the flesh, preached the Kingdom of Heaven.
Those sinners who received His commandments judge themselves in the flesh as men. That is, in the present human life they condemn their flesh to fasts, prostrations, tears, and other hardships.
They do this in order to live according to God in the spirit, being animated in this by the apostolic saying: "Though our outward man is perishing, yet the inward man is being renewed day by day" (2 Cor 4:16).