Here is an email I sent to a friend who was asking about this verse in regards to Calvinism. I used this page, as well as some other resources, so thanks! I want to share it here so others can gain from it and perhaps take some things when they need to explain the verse to their friends!
Hey! I'm glad to hear from you.
I'll start with a bit about me and what I believe. So as you know I am a Calvinist, and I'd probably label myself as a Reformed Baptist as opposed to classic Reformed (Presbyterian). Some of the people I have learned from and hold in high regard as men of God are Charles Spurgeon, John Piper, James White, RC Sproul, Paul Washer, John MacArthur, and some oldies like Jonathan Edwards, John Owen, John Calvin, A.W Pink...when it comes to their views of God sovereignty, I would be in full agreement which means that I believe God is completely and absolutely sovereign over all things, meaning that I believe everything that has happened, is happening and will happen have been ordained or predetermined by God, and yes, that includes the Fall, the entrance of sin and death into the world. This doesn't mean I believe God is the author of sin though, because along with all those men I mentioned I understand that this is a paradox, how God can be completely sovereign and yet remain blameless and sinless. We can touch more on that later though.
I have taken a long time to get to this point, trust me. It didn't happen overnight. I had to wrestle with the Bible, with my own thoughts and objections and it was tough sluggin'. I was confronted with these powerful verses, and rather than suppress them or try to explain them away, I took the time to understand the implications of what it means for God to be completely sovereign and now that I am here, God's sovereignty is a hill I would die on. I fully believe these doctrines.
So anyways, enough about me, let's deal with the text you brought up, 2 Peter 3:9. Here it is in the ESV, to see a slightly different rendering:
"The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance."
For the most part it is the same as the KJV but I will point out a couple differences. The KJV says, "but is longsuffering to us-ward" whereas the ESV has "but is patient toward you". And then the KJV says, "not willing that any should perish" and the ESV, "not wishing that any should perish". Those are the two notable differences I saw, but they are minor and I don't think they alter the meaning whatsoever.
The first thing I want to get out there is that this verse is not just a problem for the Calvinist, but for anyone who believes that the consequences of dying without the forgiveness of sins is eternal punishment in hell. As Jim McClarty puts it, "the same God that is apparently not willing that any should perish also created hell...the same God that is not willing that any should perish created an environment in Eden that would bring about the fall of mankind...the same God that is not willing that any should perish is described by the same author, Peter, as a consuming fire...the same God that is not willing any should perish judges people and sends them eternally out of his presence...". And it's not just enough to point to so-called "free will" for the reason why some do perish because if God truly wills that absolutely no one should perish, it would be so! I just wanted to get that out in the open.
Now let's do some exegesis! If you don't know, exegesis is the method of understanding and interpreting Scripture where we attempt to draw the meaning out of the text, whereas the opposite, eisogesis, is the practice of inserting meaning into the text that is not there. Exegesis is a great thing to learn and practice.
The first thing we should investigate is the pronoun we read in the verse. In the KJV, it is "us", "The Lord...is longsuffering to us" and ESV, "The Lord...is patient toward you". So who is the "you" or "us" that Peter is referring to? Who is his intended audience?
We will let Peter tell us! 2 Peter 1:1:
"To those who have obtained a faith of equal standing with ours by the righteousness of our God and Savior Jesus Christ:"
So Peter is talking to Christians, believers, God's elect. This continues right through into chapter 3:
"This is now the second letter that I am writing to you, beloved." (v.1)
Beloved is a term that either refers to Christ, or to believers. In this case, it is believers. And in that first letter, here is how he identifies his audience:
"To those who are elect exiles..." (1 Peter 1:1)
And then finally, the verse right before (2 Peter 3:8) says, "But do not overlook this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day." Again we see the word beloved. So the context of Peter's letters, the context of 2 Peter as a whole, and the context of 2 Peter 3 make it clear that Peter is talking to a group of Christian believers. So the "you" or "us" in verse 9 are Christians. The next question then is, does Peter refer to another group of people? A group that is not "us" or "you"? And yes, he does.
2 Peter 2:1-3, "But false prophets also arose among the people, just as there will be false teachers among you, who will secretly bring in destructive heresies, even denying the Master who bought them, bringing upon themselves swift destruction.2 And many will follow their sensuality, and because of them the way of truth will be blasphemed. 3 And in their greed they will exploit you with false words. Their condemnation from long ago is not idle, and their destruction is not asleep."
So there is they, false prophets and false teachers, and there is you, Christian believers.
"then the Lord knows how to rescue the godly from trials, and to keep the unrighteous under punishment until the day of judgment, 10 and especially those who indulge in the lust of defiling passion and despise authority." (v.9)
So for they, there is condemnation from long ago (v.3), and reserved punishment for the day of judgement (v.9). Notice the word "keep", the unrighteous, they, are kept under punishment, being reserved until the day of judgement. In fact, the KJV uses the word reserve, rather than keep! That does not seem to sound like God is willing that absolutely everyone should not perish! There's more:
"But these, like irrational animals, creatures of instinct, born to be caught and destroyed, blaspheming about matters of which they are ignorant, will also be destroyed in their destruction," (v.12)
So these, the same group as they, the unrighteous, are described as irrational creatures of instinct, born to be caught and destroyed. The KJV says they are "made to be taken and destroyed". Is God an irrational God who is wishing that these people who were made or born to be destroyed shall not perish?
"This is now the second letter that I am writing to you, beloved. In both of them I am stirring up your sincere mind by way of reminder,2 that you should remember the predictions of the holy prophets and the commandment of the Lord and Savior through your apostles, 3 knowing this first of all, that scoffers will come in the last days with scoffing,following their own sinful desires. 4 They will say, “Where is the promise of his coming? For ever since the fathers fell asleep, all things are continuing as they were from the beginning of creation.” 5 For they deliberately overlook this fact, that the heavens existed long ago, and the earth was formed out of water and through water by the word of God, 6 and that by means of these the world that then existed was deluged with water and perished. 7 But by the same word the heavens and earth that now exist are stored up for fire, being kept until the day of judgment and destruction of the ungodly.
8 But do not overlook this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day. 9 The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance."
Here Peter is saying that there will be people, scoffers following their own sinful desires asking, mockingly, where Christ is, since he promised to return. They will say that he won't be coming since things have been going on the same since the beginning of creation. But they overlook the fact that God destroyed the earth through water, and by the same word he did that, he is storing up fire for the destruction of the present heaven and earth and ungodly men. Then literally 2 verses later, he says that he is not willing that any should perish. So either we have an immense theological conundrum and God contradicting himself, or worse keeping people for the purpose of destruction and judgement but at the same time not wishing they should ...