The fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death. –Revelation 21:8 (KJV)

The sins of those who perish, among which are first mentioned their cowardliness and unbelief. The fearful lead the van in this black list. They durst not encounter the difficulties of religion, and their slavish fear proceeded from their unbelief. —MATTHEW HENRY’S COMMENTARY

Those who, for fear of losing life or their property, either refused to receive the Christian religion, though convinced of its truth and importance; or, having received it, in times of persecution fell away, not being willing to risk their lives. —ADAM CLARKE’S COMMENTARY