Charles H. Spurgeon on Psalms 112:10

The wicked shall see it, and be grieved; that is, he shall have secret indignation in himself to see matters go so; he shall gnash with his teeth, and melt away. Gnashing of teeth is caused by vexing the heart; and therefore it follows, he melts away; which notes (melting is from the heart) an extreme heat within. The sense is very suitable to that of Eliphaz (Job 5:2) "wrath slayeth the foolish, "or wrath makes him melt away, it melts his grease with chafing, as we say of a man furiously vexed. Hence that deplorable condition of the damned, who are cast out of the presence of God for ever, is described by "weeping, and wailing, and gnashing of teeth"; which imports not only pain, but extreme vexing at, or in themselves. These finally impenitent ones shall be slain for ever with their own wrath, as well as with the wrath of God. —Joseph Caryl.