Revelation 11:6

These have the power to shut the heaven, that it rain not during the days of their prophecy: and they have power over the waters to turn them into blood, and to smite the earth with every plague, as often as they shall desire.

The power here attributed to the witnesses is actually a reference, not to their power in themselves, but to that of their great Guardian, Benefactor, and King, the Lord himself.

Powers to shut the heaven ... This verse sends the commentators rushing to Elijah for what they think is the meaning. "He had the power to withhold rain," they say; but did he? "Was it not God's Word, not the prophet, who did this? Therefore, all of the worthies of the Old Testament, either singly or collectively, if they should come back to this earth (which none of them will ever do), would never be able to do what is mentioned here.

Powers over the waters to turn them to blood ... It is clear that what John is doing here is merely citing some of the great historical examples of wonders performed by the word of God upon behalf of his people, with the inherent deduction that the same power is still operative upon their behalf.

What is indicated here is not a capricious exercise of awesome power, but a statement that there is awesome power still available to protect and accompany the two witnesses in their proclamation of the truth. This power is not at all exercised by people, but by God himself in his providential protection of both his word and his people; and it is never exercised capriciously, but only when necessary, and always in complete harmony with God's will. The word here is not that God shall continuously exhibit such wonders, but that the power is there. "They have power" is the repeated clause here. That this great power is here said to belong to the two witnesses must not obscure the truth that the power is God's, and that it belongs to the witnesses merely in the sense of their being the true agents of God in this dispensation.