We could read the phrase as a merism describing “everyone”; that is, no one escapes the last judgment. Though that is accurate, the phrase seeks to go beyond the term “everyone”; phrases as “old and young,” “male and female,” or “rich and poor” would have caught that meaning as well. The law of the land can judge “the living,” but “the dead” are beyond its reach. That is not the case for the judgment of him who arose from the dead. With this phrase, then, Peter is describing Jesus Christ as Lord and Judge not only of the living (whoever they are and wherever they live) but also of the dead (no matter how long ago they died). He is so great a king that Death and Hades are in his hands (John 5:27–28).
5 but they will give account to him who is ready to judge the living and the dead.