Peter is helping suffering believers understand what is happening to them. "The time is come that judgment must begin at the house of God." Barnes says "judgment" here seems to mean "the severe trial which would determine character," and Gill likewise understands it not as punishment for sin but as afflictions and persecutions. Then Peter reasons from the lesser to the greater. If God's own household passes through such trials, what will the end be for those who refuse His gospel? Barnes draws out the point: if God brings such trials on those who obey His gospel, how much more may those who remain in their sins expect? The question helps believers see their suffering in a larger frame, and it sobers them about the fate of those who reject the gospel.

Peter does not spell out the answer in plain words. He presses it home with a second question, drawn from Proverbs: "if the righteous scarcely be saved, where shall the ungodly and the sinner appear?" (1 Peter 4:18). Then he turns back to the sufferers with comfort: "let them that suffer according to the will of God commit the keeping of their souls to him in well doing, as unto a faithful Creator" (1 Peter 4:19).

Barnes thinks there is probably an allusion here to the Old Testament prophets. In Ezekiel 9:6, God commands judgment on Jerusalem with the words "begin at my sanctuary." In Jeremiah 25:29, He says, "I begin to bring evil on the city which is called by my name, and should ye be utterly unpunished?" Barnes applies "the house of God" in Peter to Christians as "the house or family of God." Gill gives two possible readings: the temple at Jerusalem or the church of God.

In the Greek, "judgment" is krima, "house" is oikos (household or family), and "end" is telos, the final outcome. "Obey not" is apeitheo, to disobey.

This question reveals a pattern in God's ways: He begins with His own people. Matthew Henry observes, "When God brings great calamities and sore judgments upon whole nations, he generally begins with his own people." For believers, these trials are not a sign that God has left them. Peter has already said that their faith is being "tried with fire" so that it "might be found unto praise and honour and glory at the appearing of Jesus Christ" (1 Peter 1:7).

But the question also looks outward. If God's refining touches His own house, then those who "obey not the gospel of God" have far more reason to fear. The question is meant to steady believers and to leave no one comfortable outside of Christ.