Albert Barnes on 1 Peter 4:5

Who shall give account. That is, they shall not do this with impunity. They are guilty in this of a great wrong, and they must answer for it to God.

That is ready to judge. That is, "who is prepared to judge"-- τωετοιμωςεχοντι. See the phrase used in Acts 21:13: "I am ready not to be bound only, but also to die at Jerusalem." 2Cor 12:14 "The third time I am ready to come to you." Compare the word ready--ετοιμος in Mt 22:4,8, 24:44, 25:10, Lk 12:40, 22:33, 1Pet 1:5. The meaning is, not that he was about to do it, or that the day of judgment was near at hand--whatever the apostle may have supposed to be true on that point--but that he was prepared for it; all the arrangements were made with reference to it; there was nothing to hinder it.

To judge the quick and the dead. The living and the dead; that is, those who shall be alive when he comes, and those in their graves. This is a common phrase to denote all who shall be brought before the bar of God for judgment. Acts 10:42. 1Thes 4:16; 1Thes 4:17; 2Ti 4:1. The meaning in this connexion seems to be, that they should bear their trials and the opposition which they would meet with patiently, not feeling that they were forgotten, nor attempting to avenge themselves; for the Lord would vindicate then when he should come to judgment, and call those who had injured them to an account for all the wrongs which they had done to the children of God.

(*) "quick" "Living"