"We will briefly review the points:
1. Those only who accept Christ receive eternal life; all others 
perish. John 3:16. That is, they will be blotted from existence.
This is the penalty which was threatened in the beginning, before sin entered, and which is now simply delayed a little in order to allow mankind an opportunity to repent. Thus it is that “the long suffering of our Lord is salvation.” 2 Peter 3:15.
2. The agent by which the death penalty is to be executed,is fire—everlasting fire.
We saw that it was eternal fire that destroyed the cities of Sodom and Gomorrah,and that by means of “unquenchable fire” the walls and palaces of Jerusalem were devoured.
We learned also that the “eternal fire” that fell upon the cities of the plain turned them to ashes, and that this is what is always accomplished when fire is unquenchable.
The wicked being likened to chaff, and stubble, it does not tax our imagination in the least to understand how, when cast into unquenchable fire, they will be burned up, and be ashes.
3. We have also seen that the wicked go into “everlasting
punishment.”
punishment.”
But this punishment is death, so that Matthew 25:46 simply teaches that from the death which the finally impenitent suffer, from which there will be no resurrection."
E.J. Waggoner