And if any man will hurt them, fire proceedeth out of their mouth, and devoureth their enemies; if any one willeth to hurt them, etc. Most probably a reference to the act of Elijah (2 Kings 1:10). Perhaps there is a double reference in the fire proceeding out of their mouth; it is the fire of their witness, which refines and purifies and convinces some; it is also the fire of condemnation, which follows those who reject the testimony.
The figure is found in Jeremiah 5:14, "I will make my words in thy mouth fire, and this people wood, and it shall devour them" (see also Hosea 6:5; Ecclesiasticus 48:1). And if any man will hurt them, he must in this manner be killed; any one shall will (future) is read in the Revised Version, and is supported by א, A, 38; θέλει, (present) is found in B, C, P, Andreas, Arethas.
"In this manner;" that is, by fire. Such, throughout the Scriptures, is the form under which the final judgment of those who reject God's message is shadowed forth. The description is not more opposed to a general interpretation than it is to an individual interpretation of the two witnesses.