For if God did not spare angels when they sinned, but cast them into hell and committed them to chains of gloomy darkness to be kept until the judgment; if he did not spare the ancient world, but preserved Noah, a herald of righteousness, with seven others, when he brought a flood upon the world of the ungodly; if by turning the cities of Sodom and Gomorrah to ashes he condemned them to extinction, making them an example of what is going to happen to the ungodly; and if he rescued righteous Lot, greatly distressed by the sensual conduct of the wicked (for as that righteous man lived among them day after day, he was tormenting his righteous soul over their lawless deeds that he saw and heard); then the Lord knows how to rescue the godly from trials, and to keep the unrighteous under punishment until the day of judgment,
2 Peter 2:4-9
This is a difficult passage in its construction, and a glance at it as a whole will be necessary before dealing in detail with its various parts, so as to see the gist of Peter's argument. The starting point is the last phrase of 3 - 'whose judgment...' It is the certainty of coming judgment on the false prophets and teachers that is in the Apostle's mind, and he takes three instances from the past to prove it. The 'if' in 4 applies to each of the three illustrations and the statement in 9 completes the sentence. It is really a continuing principle that is being stated. 'This is how it has happened in the past, and this is how it will be now'. If God spared not the wicked but delivered the righteous in the past, then (9) He will deliver the godly out of temptation and reserve the unjust unto judgment today also. The thought of judgment may be grim and frightening to our minds, but it should be clear to us from this passage that if right is to be vindicated at all and wrong put down, then judgment is a necessity.