And if any man will hurt them - This implies that there would be those who would be disposed to injure or wrong them; that is, that they would be liable to persecution. The word "will" is here more than the mere sign of the future; it denotes "intention, purpose, design," θέλεὶ thelei - "if any man wills or purposes to injure them." See a similar use of the word in 1-Timothy 6:9. The word "hurt" here means to do "injury" or "injustice" - ἀδικῆσαι adikēsai - and may refer to wrong in any form - whether in respect to their character, opinions, persons, or property. The general sense is, that there would be those who would be disposed to do them harm, and we should naturally look for the fulfillment of this in some form of persecution.
Fire proceedeth out of their mouth - It is, of course, not necessary that this should be taken literally. The meaning is, that they would have the power of destroying their enemies as if fire should proceed out of their mouth; that is, their words would be like burning coals or flames. There may possibly be an allusion here to 2-Kings 1:10-14, where it is said that Elijah commanded the fire to descend from heaven to consume those who were sent to take him (compare Luke 9:54); but in that case Elijah commanded the fire to come "from heaven"; here it proceedeth "out of the mouth." The allusion here, therefore, is to the denunciations which they would utter, or the doctrines which they would preach, and which would have the same effect on their enemies as if they breathed forth fire and flame. So Jeremiah 5:14, "Because ye speak this word, Behold, I will make my words in thy mouth fire and this people wood, and it shall devour them."
And devoureth their enemies - The word "devour" is often used with reference to fire, which seems to "eat up" or "consume" what is in its way, or to "feed on" what it destroys. This is the sense of the word here - κατεσθίει katesthiei - "to eat down, to swallow down, to devour." Compare Revelation 20:9; Septuagint Isaiah 29:6; Joel 2:5; Leviticus 10:2. As there is no reason to believe that there would be literal fire, so it is not necessary to suppose that their enemies would be literally devoured or consumed. The meaning is fulfilled if their words should in any way produce an effect on their enemies similar to what is produced by fire: that is, if it should destroy their influence; if it should overcome and subdue them; if it should annihilate their domination in the world.
And if any man will hurt them - This is repeated in order to make the declaration more intensive, and also to add another thought about the effect of persecuting and injuring them.
He must in this manner be killed - That is, in the manner specified - by fire. It does not mean that he would be killed in the same manner in which the "witnesses" were killed, but in the method specified before - by the fire that should proceed out of their mouth. The meaning is, undoubtedly, that they would have power to bring down on them divine vengeance or punishment, so that there would be a just retaliation for the wrongs done them.

Fire proceedeth out of their mouth - That is, they are commissioned to denounce the judgments of God against all who would attempt to prevent them from proceeding in their ministry.

(9) And if any man will hurt them, fire proceedeth out of their mouth, and devoureth their enemies: and if any man will hurt them, he must in this manner be killed.
(9) The power and surety of the holy ministry, which is truly evangelical, is declared both in earth and in heaven, protecting the administers of it, and destroying its enemies, in this verse, divine power, most mightily showing itself forth in heaven, earth and the sea in (Revelation 11:6) as it is described in (2-Corinthians 10:4) according to the promise of Christ in (Mark 16:17). This is the second place (as I said before) of the combats which the servants of God must undergo in the executing of their calling, and of the things that follow the same combats or conflicts are these things to overcome, in these two verses: to be overcome and killed in (Revelation 11:7) After the slaughter follow these things, that the carcasses of the godly, laid abroad in (Revelation 11:8) and being unburied, are scorned, together with cursing and bitter abhorrance (Revelation 11:9) and that therefore congratulations are publicly and privately made in (Revelation 11:10).

And if any man will hurt them,.... Do any injury to their persons, or properties, oppose their writings, blaspheme their doctrines, and hinder their ministrations; whoever; they be, whether they be any that live among them, or in other parts; whether they be secret or open enemies; or whether they be of the outward court, or be really Gentiles or Papists; and especially if they do them any injustice, if they wrong, oppress, afflict, and distress them knowingly and willingly:
fire proceedeth out of their mouth; by which may be meant the word of God, which they preach and hold forth, which is comparable to fire, Jeremiah 23:29, both for light, it being a means of enlightening sinners, who are darkness itself; and of directing saints in their walk and conversation; and of detecting the errors, immoralities, idolatry, and superstition of men, and particularly of the church of Rome, who cannot bear the light of this word, and therefore forbid the reading of it to the laity, and keep it locked up from them in the Latin tongue: and also for the heat of it, it being the means of quickening, or of conveying a vital heat to dead sinners; and of warming and comforting the saints, causing their hearts to burn within them, while they bear or read it, or meditate upon it; and of scorching and tormenting reprobate sinners, and filling them with wrath, pain, and anguish, especially the followers of antichrist; and this is greatly designed, for this has a particular reference to the pouring out of the fourth vial, Revelation 16:9. Likewise, the word of God may be compared to fire for its purity in itself, for every word of his is pure; and for its purifying nature, when faithfully preached, and powerfully applied, it penetrates deep, it searches, and discovers, and purges from the dross of profaneness, false doctrine, and will worship; and for its consuming nature, as follows, it pronouncing damnation to unbelievers and impenitent sinners, and it being the savour of death unto death to such: or else the prayers of these witnesses are intended by the fire that proceeds out of their mouth, for vengeance on their enemies, who hinder their ministrations, blaspheme the truth, and shed their blood; which do not arise from a passionate and revengeful spirit, but from a pure zeal for the glory of God, and the honour of his name, and truth; and which prayers are heard by God, who will avenge his elect, that cry unto him day and night: the allusion is to the fire, which, at the request of Moses, came forth from the Lord, and destroyed two hundred and fifty persons, that opposed him and Aaron; and to the fire which Elias called for from heaven, upon the captains, and the fifties, that came to take him, who were types of these witnesses; see Numbers 16:3. And also this fire may denote the denunciations of God's wrath by them upon the antichristian party, these being as wood, and their words as fire, to consume them; see Jeremiah 5:14.
And devoureth their enemies: whether open or secret; just as the fire devoured Nadab and Abihu, the offerers of strange fire, which the Lord commanded not; so the fire out of the mouth of God's faithful servants devours such who introduce divers and strange doctrines, and the inventions of men, into the church of God; the light of God's word convinces and confounds them, though it may not convert them; it flashes in their consciences, and distresses them, so that they gnaw their tongues for pain; there being nothing but a fearful looking for of judgment, and fiery indignation, which shall devour and destroy them, though not corporeally, yet spiritually and eternally; for even these shall afterwards make war against them, conquer them, and slay them, and shall see them ascend to heaven, Revelation 11:7.
And if any man will hurt them, he must in this manner be killed; this is repeated, partly to show the certainty of this destruction; and partly to point out the manner of it, which will be not by the use of carnal weapons: these enemies of the witnesses will not be killed by the sword, or any other weapon, but by the word of God, and through the prayers of the saints, and by the denunciations of God's judgments on them. The Jews express the doctrines and traditions of their Rabbins, delivered from one to another, by fire, proceeding out of their mouths; who say (r),
"Rab sat before Rabbi, and "there went forth" , "sparks of fire from the mouth of Rab", into the mouth of Rabbi, and from the mouth of Rabbi, into the mouth of Rab;''
which the gloss explains of their communicating their doctrines and traditions to one another.
(r) T. Bab. Cholin, fol. 137. 2. Juchasin, fol. 113. 2.

will hurt--Greek, "wishes," or "desires to hurt them."
fire . . . devoureth--(Compare Jeremiah 5:14; Jeremiah 23:29).
out of their mouth--not literally, but God makes their inspired denunciations of judgment to come to pass and devour their enemies.
if any man will hurt them--twice repeated, to mark the immediate certainty of the accomplishment.
in this manner--so in like manner as he tries to hurt them (compare Revelation 13:10). Retribution in kind.

Fire proceedeth out of their mouth. Whatever is signified by these two witnesses, they have the power to destroy. In seeking for the two witnesses we must find agencies which can save life and can destroy it, can shut the heavens and open them, can prevent blessings from descending upon the earth, can inflict curses and plagues on the inhabitants of the earth. The witnesses have supernatural powers.

If any would kill them - As the Israelites would have done Moses and Aaron, Numbers 16:41. He must be killed thus - By that devouring fire.