On Revelation 11:4...
Observe here, 1. A double title given by God unto the two witnesses, spoken of in the former verse; they are styled olive-trees and candlesticks. As the olive-tree is always green, so the ministry of these witnesses is lively and efficacious; as the olive is a sign of peace, and the oil that drops from the olive an emblem of grace, so the ministry of these witnesses was a ministry both of grace and peace. Again, they are called olive-trees, because they are to minister oil to the candlesticks, which are to hold out light unto others.
Here note, That the title of candlesticks given to the churches, chap. 1 is here given to the ministers of the church; partly to show the near relation that is between them, and partly to point out the duty that is mutually incumbent upon them; namely, to hold forth the light of truth unto others.
And farther, these candlesticks are said to stand before the God of the earth, signifying their fidelity in the discharge of their duty, as in the presence of God, before whom they stand.
Observe, 2. The efficacy and power of these witnesses' ministry in the certain effects of it. What was said of Elijah and Elisha literally, is applied unto them spiritually.
1. As Elijah brought fire down from heaven, which devoured the enemy, so fire proceeds out of these witnesses' mouth, not by way of imprecation, but by way of denunciation, pronouncing the threatenings and judgments of God against them, continuing in their impenitency.
2. As Elijah had power to shut heaven, so have these witnesses power to do the like during the time of their prophecy; that is, God is provoked for the world's ill treatment of his faithful witnesses to withhold the spiritual rain of the word, and the refreshing doctrine of the gospel, from them.
Again, when it is said that these witnesses have power to turn the waters into blood, and to smite the earth with all plagues, there is a manifest allusion to Moses and Aaron, who exercised such a power. Exodus 7:1-25.
Accordingly, God being provoked by the indignities offered to his faithful witnesses, permits the pure doctrine of the gospel to be corrupted, and avenges their cause, by bringing judgments on the world, as Moses did upon Egypt, according to the threatenings denounced by them.
Whence we may learn, what great credit and esteem the faithful witnesses and ministers of Christ are in with God; what power and prerogative is given to them, far surpassing the power of any mortal prince, even a power to open and shut heaven, to turn waters into blood, and to smite the earth: that is, God doth all these things upon a just occasion in vindication of them, and in revenge for the injuries done unto them.
Source of info- William Burkitt's Expository Notes