Verses 1 - 2
"...a reed like unto a rod..."
This chapter opens with the same angel of chapter 10, giving John a reed like a measuring rod, and telling him to measure the temple of God. This is to be done in order to determine the size, relative to the number of people worshipping there. Is it sparsely occupied, or is it nearly full?
The time for all things to be fulfilled is drawing nigh, and a measurement is now taken to determine where the people stand in their relationship to God.
This temple has to be the newly built temple in Jerusalem at the time of the tribulation period, and not the heavenly temple, because it is stated that the outer court is given to the Gentiles. It is also stated that they shall tread the Holy City under foot for 42 months (3 1/2 years). This is the same time period set for the Antichrist to exercise his power {13:5}.
Verses 3 - 6
"...two witnesses..."
As we discovered in chapter 10, these two men were depicted as being the feet of the angel and appeared as "pillars of fire". They are to give testimony for a period of 1,260 days (42 months x 30 days) clothed in sackcloth; the garment of the prophets of old.
In verse 4, they are also identified as the "two olive trees" and the "two candlesticks" which stand before the God of the earth. This is an obvious reference to Zechariah 4:3,14, and helps us to understand that these two burning lampstands come down to earth as the "pillars of fire".
In that chapter, they appear as two olive trees, and also as two olive branches. The two branches drip oil into two bowls from which pipes run to a third bowl, sitting on top of a golden lampstand. The third bowl provides the fuel for the seven lamps attached to the golden lampstand, through seven pipes which extend out of the bowl.
Verse 14 tells us that these are "...the two annointed ones that stand by the Lord of the whole earth." Verse 3 indicates that these two are standing to the left and to the right of the golden lampstand. The golden lampstand would therefore, represent the Lord of the whole earth or the throne upon which He sits, since we are told in verse 14 that these two stand beside Him. This chapter also has us to know that the seven lamps (verse 2) are the "...eyes of the Lord, which run to and fro through the whole earth." This is comparable to {Rev. 4:5} and {Rev. 5:6}
In Rev 11:4, we see these two "...standing before the God of the earth" rather than beside Him, indicating that they have moved out of their customary positions and are ready to go forth on their mission in the earth.
"...fire proceedeth out of their mouth..."
God has equipped these two with special powers of protection, so that anyone who seeks to thwart their mission will be dealt with in a swift and most undesirable manner. Though attempts will be made to take their lives, all will result in failure until they have finished the testimony for which they were sent into the world to deliver. The fire coming from their mouths speaks of judgment sanctioned and executed from heaven.
"...power to shut heaven..."
Verse 6 reveals a couple of things which point us to the idea that these two are Moses and Elijah.
That no rain falls in the days of their prophecy (3 1/2 years), reminds us that the first judgment recorded in the Bible, as related to the Prophet Elijah, was that he prayed and no rain fell in the land {I Kings 17:1}.
In Luke 4:25, Jesus stated that in the days of Elijah, "...the heaven was shut up three years and six months, when great famine was throughout all the land." James 5:17-18 speaks of the same event.
Malachai 4:5 also tells us that God will send the prophet Elijah "...before the coming of the great and dreadful day of the Lord."
John the Baptist indeed came in the spirit of Elijah (Luke 1:17), but Elijah himself will return to this world before the Revelation of Jesus Christ.
Indeed, the Jewish people also believe that Elijah will come in advance of Messiah to prepare the world for his arrival. By Jewish custom, a place in every home is reserved for Elijah, at each Passover, in hopes that he will make his appearance and usher in the Messianic age.
"...power over the waters to turn them to blood..." recalls that the first judgment of God wrought through the hands of Moses, before Pharoah, was changing the water of the Nile River into blood (Exodus 7:14-24).
These two have power to smite the earth with any judgments they choose, and as often as they deem them necessary. These judgments appear to be in addition to those which are poured out as the "wrath of God" in the Book of Revelation.
Scripture implies that because of the afflictions brought on by the plagues released by them, at least some attempts will be made on their lives. The inability of the world to stop them will bring great anguish upon all those who oppose their message.
God is going to restore the Law and the Prophets through these two witnesses, as a testimony to Israel and the world, that all things contained therein point to Jesus as the true Messiah.
In Rev. 12:17 we are told of those which, "...keep the commandments of God and have the testimony of Jesus Christ." They keep the Law, and now understand and receive the fact that all the prophets of God pointed to the coming of Jesus Christ as the Messiah.
When Jesus was transfigured (Matt. 17:1-3; Mark 9:2-4; Luke 9:28-30) it was Moses and Elijah who appeared with Him.