During our prayer meeting Wednesday, someone brought up 2 Peter 3:8-9, which says, "But do not let this one fact escape your notice, beloved, that with the Lord one day is like a thousand years, and a thousand years like one day. The Lord is not slow about His promise, as some count slowness, but is patient toward you, not wishing for any to perish but for all to come to repentance." These wonderful words were written by Peter under the inspiration of God to show believers why God has waited so long to send Jesus back to earth. Although I wish he would have explained it, Peter's point here is not to explain the difference between the wish and will of God. As D. Martin Lloyd Jones will explain below, Peter gives practical reasons for God's long-suffering toward sinful people.
God takes no delight in the death of the ungodly; that is why, Peter says, He delays His action. That is something which we can illustrate from Old Testament history. Did you notice the times before the flood—how God seemed not to act for one hundred and twenty years? There was Noah preaching to those people. Why didn't God destroy them at the beginning, you ask? Ah, that is the long-suffering of God. God, by thus holding back His hand does not wish that the ungodly should perish. God always warns before He strikes, and if you read your Old Testament history again from this standpoint, it will amaze you more and more to notice the extraordinary patience of God. …
It is this long-suffering of God that leaves the world without an excuse or a plea. And that, according to the Apostle Peter, is the explanation of why the Lord has not returned before this particular point in history. The world is being given a chance, an opportunity; Christ is preached, the Gospel is offered; all these years are passing and the offer is being made. … God will be able to say, 'The Gospel was preached, Christ was offered to you and throughout all these long centuries I waited, I delayed, I gave you the opportunity.' The righteousness of God will be revealed. The world will be left without a vestige of an excuse. Thank God that there has been this delay. Where would you and I have been had it not been for it?
D. M. Lloyd-Jones, Expository Sermons on 2 Peter, (Carlisle, Pennsylvania: The Banner of Truth Trust, 1983), 182-3.