Matthew Hafenreffer opines-
“They are the most exquisite pains of soul and body (for both had sinned), arising from the fear and sense of the most just wrath and vengeance of God against sins, the most sad consciousness of which they carry about with them, the baseness of which is manifest, and of which, likewise, no remission afterwards, and, therefore, no mitigation or end can be hoped for. Whence, in misery, they will execrate, with horrible lamentation and wailing, their former impiety, by which they carelessly neglected the admonitions of their brethren and all the means of attaining salvation; but in vain.
For in perpetual anguish, with dreadful trembling, in shame, confusion, and ignominy, in inextinguishable fire, in weeping and gnashing of teeth, amidst that which is eternal and terrible, torn away from the grace and favor of God, they must quake among devils, and will be tortured without end to eternity. These future torments of the damned far surpass all the penetration of the human mind, so that we are not sufficient to ever comprehend in thought their greatness; therefore, what they will be, or of what nature, cannot be at all expressed in words. Scripture, nevertheless, in order to show that these tortures are the greatest and most exquisite, likens them to those things by which, in this life, pain both of soul and body is accustomed to be excited.
For this reason they are compared now to the gnashing of teeth, now to worms, now to the most sorrowful darkness, and whatever other matters of sadness and of the most complete pain can be mentioned, Is. 66:24; Matt. 5:22; 8:12; Rev. 19:20.”*
*Heinrich Schmid, The Doctrinal Theology of the Evangelical Lutheran Church, Verified from the Original Sources (trans. Charles A. Hay and Henry E. Jacobs; Second English Edition, Revised according to the Sixth German Edition.; Philadelphia, PA: Lutheran Publication Society, 1889), 659–660.