John the Apostle
Revelation 21:8ESV·traditional attribution

But as for the cowardly, the faithless, the detestable, as for murderers, the sexually immoral, sorcerers, idolaters, and all liars, their portion will be in the lake that burns with fire and sulfur, which is the second death.”

Matthew Henry Presbyterian @wholebiblehenry

We have here a more general account of the happiness of the church of God in the future state, by which it seems most safe to understand the heavenly state. I. A new world now opens to our view (Rev 21:1): I saw a new heaven and a new earth; that is, a new universe; for we suppose the world to be made up of heaven and earth.

Commenting on Revelation 21:1-8

John Gill Reformed Baptist @doctorgill

But the fearful,.... Not the timorous sheep and lambs of Christ, the dear children of God, who are sometimes of a fearful heart, on account of sin, temptation, and unbelief; but such who are of cowardly spirits, and are not valiant for the truth, but who, through fear of men, either make no profession of Christ and his Gospel, or having made it, drop it...

Albert Barnes Presbyterian @notesbybarnes

Verse 8. But the fearful. Having stated, in general terms, who they were who would be admitted into that blessed world, he now states explicitly who would not. The fearful denote those who had not firmness boldly to maintain their professed principles, or who were afraid to avow themselves as the friends of God in a wicked world. They stand in contrast with those who "overcome," . And unbelieving.