2 Peter 3:10-11
“But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up. Seeing then that all these things shall be dissolved, what manner of persons ought ye to be in all holy conversation and godliness,”
The Day of the Lord is the first day of the Millennium. The one-thousand year reign of Christ where everyone will be in their true body which is their spiritual body that feels no pain and fails to see the effects of age. How is this going to happen? The destruction of this age will be by fire. Christ told us this in the parable of the tares of the field, how the tares who are the children of Satan were bound and cast into the fire. But the wheat of our Father, those who love Him are gathered and placed into the barn. We want to be that righteous wheat my friends.
There is nothing to fear in this verse. If God loves you, you will not be burned. What happened to the three in the fiery furnace that was heated seven times hotter than necessary? Not a thing, the smell of smoke did not even pass onto their clothes though they were inside the burning furnace. Why? Because the Lord Jesus Christ was with them.