Who are the two witnesses in the book of Revelation?

These are men who appear near the middle of the tribulation period, specifically in Israel.

Revelation 11:3. “And I will give [power] unto my two witnesses, and they shall prophesy a thousand two hundred [and] threescore days, clothed in sackcloth.”

During the first 3 1/2 years of the 7 year period (a thousand two hundred [and] threescore days) 70th week of Daniels prophecy, God will send two witnesses to speak and witness on the earth 7 year period called 'the times of Jacobs trouble' or 'the tribulation period'

Can the two witnesses of Rev.11 be Enoch, Elijah or Moses?

A good point is that Jesus said Elijah must come before the great and terrible day of the Lord. But if Elijah entered heaven physically as the Bible teaches, then he must have had a bodily change from corruptible to incorruptible, for flesh and blood cannot enter the kingdom of heaven. This means he had a transformation to his body (as did Enoch who entered without dying Heb.11).

We would have to believe that God would reverse their incorruptible bodies, from being sinless to sinful so they can be killed for the first time.

Both Elijah and Moses according to Judaism were the two most powerful prophets in the Old Testament. Elijah was known for his miracles and Moses delivered the law. Both represented a good portion of all the prophets. This is why we these two and no others are at the Mount of Transfiguration when Jesus revealed His glory and what the kingdom would be like to his closest disciples.
Many believe the two witnesses will either be Enoch, Elijah and Moses because of how they dress (in sackcloth). Elijah is usually a main candidate as one of the witnesses because he did not see death but was carried to heaven on a heavenly chariot. Because the miracles done by the two witnesses are similar to Moses and Elijah most people assume it must be them.

But why can’t these be two completely new witnesses and prophets?

I don't think that the two witnesses will be either Moses or Elijah. First, Elijah was brought to heaven bodily so he has an immortal body that can never die again, once God gives this body it is permanent. If he is transformed then he is unable to die.

Not Moses because flesh and blood cannot enter heaven with their body so he must be transformed also. Moses would have had to have a separate resurrection which the Bible does not speak of to be the other witness. I do not think Moses would be resurrected and then die again in the Tribulation? The Bible never mentions Moses coming back in the Tribulation. One would think it would be worth mentioning if such an important event takes place; if Moses or any other Old Testament Saint would be here for years.

No one really knows for sure who the two witnesses will be. I would suggest they may be someone completely new that act in a similar manner, just as John the Baptizer did with Elijah. Two completely new witnesses, as God often does things this way. We don't see him recycle prophets from the Old Testament anywhere else.

The two witnesses will speak their message dressed in sackcloth. They will give a message of repentance and salvation and the sackcloth is a sign of the importance to Israel. John the Baptist wore sackcloth when he gave his message. likewise this is done just before the lord is to come again . Sackcloth also means separation from the world a sign for repentance, to seek God's mercy (Jonah 3:5-6; Dan.9:3; Esther 4:1; Amos 8:10; Mt.11:21).

God will use these two witnesses specifically to Israel as he will have the sealed 144,000 Jews from the tribes of Israel to proclaim the Gospel to the world. They will take over the job of proclaiming the Gospel from the Church which will be in heaven during this time. An innumerable number of souls will be won to the Lord Jesus during the tribulation period.

The Bible tells us Rev.11:4 “These are the two olive trees, and the two candlesticks standing before the God of the earth.

V.5 “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.”

These men were prophesied in the Old Testament Zech. 4:3-11, 14 “These are the two anointed ones, who stand beside the Lord of the whole earth.”

God wants his people to hear the Gospel and respond and be saved. In the end He will not allow their message to be interfered with by anyone. The two witnesses will be free to proclaim the Gospel and the devil or his servants are unable to stop them even though their power will be increased on the earth (until God allows it).

V.6 “These have power to shut heaven, that it rain not in the days of their prophecy: and have power over waters to turn them to blood, and to smite the earth with all plagues, as often as they will.”
During the seven year tribulation period, specifically, the first 3 1/2 years there will be no rain in Israel. Imagine what that will do the environment. No wonder people want them dead.

The two witnesses also turn the waters to blood, and bring plagues. They are God’s hand of judgment till men repent.

V.7 “And when they shall have finished their testimony, the beast that ascendeth out of the bottomless pit shall make war against them, and shall overcome them, and kill them.”

There are two beasts mentioned. At the end of the first 3 1/2 years the two witnesses mission will be done. Only at this time does God allow them to be killed. The Devil will get his way.

V.8 “And their dead bodies [shall lie] in the street of the great city, which spiritually is called Sodom and Egypt, where also our Lord was crucified.”

The two witnesses will be killed in the city of Jerusalem that will be filled with sin and bondage (thus the correlation to Sodom and Egypt) ...the same city the Lord Jesus Christ was crucified. Their deaths will be covered world-wide by all the media.

V.9 “And they of the people and kindreds and tongues and nations shall see their dead bodies three days and an half, and shall not suffer their dead bodies to be put in graves.”10 And they that dwell upon the earth shall rejoice over them, and make merry, and shall send gifts one to another; because these two prophets tormented them that dwelt on the earth.”

They did not repent at their message the people will party like it’s the end of the world. Their bodies will be on open display through the media to the world for 3 1/2 days. The people of the world will rejoice that these two prophets of God are killed, this will be like the worlds Christmas present.

Certainly this even will contribute to the people saying “who is able to make war with the beast”(Rev.13) which leads up to the antichrist entering the rebuilt Temple in Jerusalem and proclaim he is God demand worshiping from those there and throughout the world.

V.11 And after three days and an half the breath of life from God entered into them, and they stood upon their feet; and great fear fell upon them which saw them. 12 And they heard a great voice from heaven saying unto them, Come up hither. And they ascended up to heaven in a cloud; and their enemies beheld them. 13 And the same hour was there a great earthquake, and the tenth part of the city fell, and in the earthquake were slain of men seven thousand: and the remnant were affrighted, and gave glory to the God of heaven....