What does 2 Peter 2:6 mean?

Peter continues his list of "if" statements, citing examples of God's judgment against those who rebel against Him. He is making the case that God will also bring the same kind of judgment against the false teachers in the church.

After mentioning God's judgment of the rebellious angels, then that of the entire world except for Noah and his family during the flood, Peter now points to the example of the cities of Sodom and Gomorrah (Genesis 19:1–29). In response to the sinfulness of the people of those cities, God sent fire from the sky to destroy both towns and all of their residents.

We generally associate Sodom with the sin of homosexuality, which was the most pervasive and famous of their errors. But Ezekiel described the wickedness of her people in much greater detail, saying they "…had pride, excess of food, and prosperous ease, but did not aid the poor and needy. They were haughty and did an abomination before me. So I removed them…" (Ezekiel 16:49–50). Modern culture has much in common with these ancient people.

Again, Peter uses an example in which God's judgment on those in rebellion was sudden and unexpected, offering no chance of escape (Proverbs 29:1). But as we see in the next verse, the righteous Judge has offered mercy in the form of a warning to those He wants to save. Peter will soon make the same connection for his readers: God's judgment is coming, but He offers salvation to those who trust in Christ.