John Calvin Commentary 2 Peter 3:7

"but the heavens that now are, and the earth, by the same word have been stored up for fire, being reserved against the day of judgment and destruction of ungodly men." — 2 Peter 3:7 (ASV)

But the heavens and the earth which are now. He does not infer this as the consequence; for his purpose was no other than to dispel the craftiness of scoffers concerning the perpetual state of nature. We see many such today who, being slightly imbued with the rudiments of philosophy, only pursue profane speculations in order that they may pass themselves off as great philosophers.

But it is now quite evident from what has been said that there is nothing unreasonable in the Lord's declaration that the heaven and the earth will in the future be consumed by fire, because the reason for the fire is the same as that for the water. For it was a common saying even among the ancients that from these two chief elements all things have originated. But as he was addressing the ungodly, he speaks explicitly of their destruction.