Albert Barnes Commentary Luke 21:26

"men fainting for fear, and for expectation of the things which are coming on the world: for the powers of the heavens shall be shaken." — Luke 21:26 (ASV)

Men's hearts failing them. This is an expression denoting the highest terror. The word rendered failing commonly denotes to die, and here it means that the terror would be so great that men would faint and be ready to die in view of the approaching calamities. And if this was true regarding the judgments about to come upon Judea, how much more so will it be in the day of judgment, when the wicked will be arraigned before the Son of God, and when they will have before them the prospect of the awful sufferings of hell—the pains and woes which will continue forever! It will be no wonder, then, if they call on the rocks and mountains to hide them from the face of God, and if their hearts sink within them at the prospect of eternal suffering.