These two men will be Moses and Elijah. Moses was given the ability to turn water into blood at the first plague where he turned the Nile River red
Exodus 7:14-25 King James Version (KJV)
14 And the Lord said unto Moses, Pharaoh's heart is hardened, he refuseth to let the people go.
15 Get thee unto Pharaoh in the morning; lo, he goeth out unto the water; and thou shalt stand by the river's brink against he come; and the rod which was turned to a serpent shalt thou take in thine hand.
16 And thou shalt say unto him, The Lord God of the Hebrews hath sent me unto thee, saying, Let my people go, that they may serve me in the wilderness: and, behold, hitherto thou wouldest not hear.
17 Thus saith the Lord, In this thou shalt know that I am the Lord: behold, I will smite with the rod that is in mine hand upon the waters which are in the river, and they shall be turned to blood.
18 And the fish that is in the river shall die, and the river shall stink; and the Egyptians shall lothe to drink of the water of the river.
19 And the Lord spake unto Moses, Say unto Aaron, Take thy rod, and stretch out thine hand upon the waters of Egypt, upon their streams, upon their rivers, and upon their ponds, and upon all their pools of water, that they may become blood; and that there may be blood throughout all the land of Egypt, both in vessels of wood, and in vessels of stone.
20 And Moses and Aaron did so, as the Lord commanded; and he lifted up the rod, and smote the waters that were in the river, in the sight of Pharaoh, and in the sight of his servants; and all the waters that were in the river were turned to blood.
21 And the fish that was in the river died; and the river stank, and the Egyptians could not drink of the water of the river; and there was blood throughout all the land of Egypt.
22 And the magicians of Egypt did so with their enchantments: and Pharaoh's heart was hardened, neither did he hearken unto them; as the Lord had said.
23 And Pharaoh turned and went into his house, neither did he set his heart to this also.
24 And all the Egyptians digged round about the river for water to drink; for they could not drink of the water of the river.
25 And seven days were fulfilled, after that the Lord had smitten the river.
This same ability will belong to the two witnesses
Revelation 11:6 King James Version (KJV)
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.
Elijah had the ability to pray and make the sky stop giving rain, just like the two witnesses:
1 Kings 17 King James Version (KJV)
1 And Elijah the Tishbite, who was of the inhabitants of Gilead, said unto Ahab, As the Lord God of Israel liveth, before whom I stand, there shall not be dew nor rain these years, but according to my word.
2 And the word of the Lord came unto him, saying,
3 Get thee hence, and turn thee eastward, and hide thyself by the brook Cherith, that is before Jordan.
4 And it shall be, that thou shalt drink of the brook; and I have commanded the ravens to feed thee there.
5 So he went and did according unto the word of the Lord: for he went and dwelt by the brook Cherith, that is before Jordan.
6 And the ravens brought him bread and flesh in the morning, and bread and flesh in the evening; and he drank of the brook.
7 And it came to pass after a while, that the brook dried up, because there had been no rain in the land.
8 And the word of the Lord came unto him, saying,
9 Arise, get thee to Zarephath, which belongeth to Zidon, and dwell there: behold, I have commanded a widow woman there to sustain thee.
10 So he arose and went to Zarephath. And when he came to the gate of the city, behold, the widow woman was there gathering of sticks: and he called to her, and said, Fetch me, I pray thee, a little water in a vessel, that I may drink.
11 And as she was going to fetch it, he called to her, and said, Bring me, I pray thee, a morsel of bread in thine hand.
12 And she said, As the Lord thy God liveth, I have not a cake, but an handful of meal in a barrel, and a little oil in a cruse: and, behold, I am gathering two sticks, that I may go in and dress it for me and my son, that we may eat it, and die.
13 And Elijah said unto her, Fear not; go and do as thou hast said: but make me thereof a little cake first, and bring it unto me, and after make for thee and for thy son.
14 For thus saith the Lord God of Israel, The barrel of meal shall not waste, neither shall the cruse of oil fail, until the day that the Lord sendeth rain upon the earth.
15 And she went and did according to the saying of Elijah: and she, and he, and her house, did eat many days.
16 And the barrel of meal wasted not, neither did the cruse of oil fail, according to the word of the Lord, which he spake by Elijah.
17 And it came to pass after these things, that the son of the woman, the mistress of the house, fell sick; and his sickness was so sore, that there was no breath left in him.
18 And she said unto Elijah, What have I to do with thee, O thou man of God? art thou come unto me to call my sin to remembrance, and to slay my son?
19 And he said unto her, Give me thy son. And he took him out of her bosom, and carried him up into a loft, where he abode, and laid him upon his own bed.
20 And he cried unto the Lord, and said, O Lord my God, hast thou also brought evil upon the widow with whom I sojourn, by slaying her son?
21 And he stretched himself upon the child three times, and cried unto the Lord, and said, O Lord my God, I pray thee, let this child's soul come into him again.
22 And the Lord heard the voice of Elijah; and the soul of the child came into him again, and he revived.
23 And Elijah took the child, and brought him down out of the chamber into the house, and delivered him unto his mother: and Elijah said, See, thy son liveth.
24 And the woman said to Elijah, Now by this I know that thou art a man of God, and that the word of the Lord in thy mouth is truth.
1 Kings 18 King James Version (KJV)
1 And it came to pass after many days, that the word of the Lord came to Elijah in the third year, saying, Go, shew thyself unto Ahab; and I will send rain upon the earth.
2 And Elijah went to shew himself unto Ahab. And there was a sore famine in Samaria.
3 And Ahab called Obadiah, which was the governor of his house. (Now Obadiah feared the Lord greatly:
4 For it was so, when Jezebel cut off the prophets of the Lord, that Obadiah took an hundred prophets, and hid them by fifty in a cave, and fed them with bread and water.)
5 And Ahab said unto Obadiah, Go into the land, unto all fountains of water, and unto all brooks: peradventure we may find grass to save the horses and mules alive, that we lose not all the beasts.
6 So they divided the land between them to pass throughout it: Ahab went one way by himself, and Obadiah went another way by himself.
7 And as Obadiah was in the way, behold, Elijah met him: and he knew him, and fell on his face, and said, Art thou that my lord Elijah?
8 And he answered him, I am: go, tell thy lord, Behold, Elijah is here.
9 And he said, What have I sinned, that thou wouldest deliver thy servant into the hand of Ahab, to slay me?
10 As the Lord thy God liveth, there is no nation or kingdom, whither my lord hath not sent to seek thee: and when they said, He is not there; he took an oath of the kingdom and nation, that they found thee not.
11 And now thou sayest, Go, tell thy lord, Behold, Elijah is here.
12 And it shall come to pass, as soon as I am gone from thee, that the Spirit of the Lord shall carry thee whither I know not; and so when I come and tell Ahab, and he cannot find thee, he shall slay me: but I thy servant fear the Lord from my youth.
13 Was it not told my lord what I did when Jezebel slew the prophets of the Lord, how I hid an hundred men of the Lord's prophets by fifty in a cave, and fed them with bread and water?
14 And now thou sayest, Go, tell thy lord, Behold, Elijah is here: and he shall slay me.
15 And Elijah said, As the Lord of hosts liveth, before whom I stand, I will surely shew myself unto him to day.
16 So Obadiah went to meet Ahab, and told him: and Ahab went to meet Elijah.
17 And it came to pass, when Ahab saw Elijah, that Ahab said unto him, Art thou he that troubleth Israel?
18 And he answered, I have not troubled Israel; but thou, and thy father's house, in that ye have forsaken the commandments of the Lord, and thou hast followed Baalim.
19 Now therefore send, and gather to me all Israel unto mount Carmel, and the prophets of Baal four hundred and fifty, and the prophets of the groves four hundred, which eat at Jezebel's table.
20 So Ahab sent unto all the children of Israel, and gathered the prophets together unto mount Carmel.
21 And Elijah came unto all the people, and said, How long halt ye between two opinions? if the Lord be God, follow him: but if Baal, then follow him. And the people answered him not a word.
22 Then said Elijah unto the people, I, even I only, remain a prophet of the Lord; but Baal's prophets are four hundred and fifty men.
23 Let them therefore give us two bullocks; and let them choose one bullock for themselves, and cut it in pieces, and lay it on wood, and put no fire under: and I will dress the other bullock, and lay it on wood, and put no fire under:
24 And call ye on the name of your gods, and I will call on the name of the Lord: and the God that answereth by fire, let him be God. And all the people answered and said, It is well spoken.
25 And Elijah said unto the prophets of Baal, Choose you one bullock for yourselves, and dress it first; for ye are many; and call on the name of your gods, but put no fire under.
26 And they took the bullock which was given them, and they dressed it, and called on the name of Baal from morning even until noon, saying, O Baal, hear us. But there was no voice, nor any that answered. And they leaped upon the altar which was made.
27 And it came to pass at noon, that Elijah mocked them, and said, Cry aloud: for he is a god; either he is talking, or he is pursuing, or he is in a journey, or peradventure he sleepeth, and must be awaked.
28 And they cried aloud, and cut themselves after their manner with knives and lancets, till the blood gushed out upon them.
29 And it came to pass, when midday was past, and they prophesied until the time of the offering of the evening sacrifice, that there was neither voice, nor any to answer, nor any that regarded.
30 And Elijah said unto all the people, Come near unto me. And all the people came near unto him. And he repaired the altar of the Lord that was broken down.
31 And Elijah took twelve stones, according to the number of the tribes of the sons of Jacob, unto whom the word of the Lord came, saying, Israel shall be thy name:
32 And with the stones he built an altar in the name of the Lord: and he made a trench about the altar, as great as would contain two measures of seed.
33 And he put the wood in order, and cut the bullock in pieces, and laid him on the wood, and said, Fill four barrels with water, and pour it on the burnt sacrifice, and on the wood.
34 And he said, Do it the second time. And they did it the second time. And he said, Do it the third time. And they did it the third time.
35 And the water ran round about the altar; and he filled the trench also with water.
36 And it came to pass at the time of the offering of the evening sacrifice, that Elijah the prophet came near, and said, Lord God of Abraham, Isaac, and of Israel, let it be known this day that thou art God in Israel, and that I am thy servant, and that I have done all these things at thy word.
37 Hear me, O Lord, hear me, that this people may know that thou art the Lord God, and that thou hast turned their heart back again.
38 Then the fire of the Lord fell, and consumed the burnt sacrifice, and the wood, and the stones, and the dust, and licked up the water that was in the trench.
39 And when all the people saw it, they fell on their faces: and they said, The Lord, he is the God; the Lord, he is the God.
40 And Elijah said unto them, Take the prophets of Baal; let not one of them escape. And they took them: and Elijah brought them down to the brook Kishon, and slew them there.
41 And Elijah said unto Ahab, Get thee up, eat and drink; for there is a sound of abundance of rain.
42 So Ahab went up to eat and to drink. And Elijah went up to the top of Carmel; and he cast himself down upon the earth, and put his face between his knees,
43 And said to his servant, Go up now, look toward the sea. And he went up, and looked, and said, There is nothing. And he said, Go again seven times.
44 And it came to pass at the seventh time, that he said, Behold, there ariseth a little cloud out of the sea, like a man's hand. And he said, Go up, say unto Ahab, Prepare thy chariot, and get thee down that the rain stop thee not.
45 And it came to pass in the mean while, that the heaven was black with clouds and wind, and there was a great rain. And Ahab rode, and went to Jezreel.
46 And the hand of the Lord was on Elijah; and he girded up his loins, and ran before Ahab to the entrance of Jezreel.
Revelation 11:6 King James Version (KJV)
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.
Elijah also destroyed people with fire:
2 Kings 1 King James Version (KJV)
1 Then Moab rebelled against Israel after the death of Ahab.
2 And Ahaziah fell down through a lattice in his upper chamber that was in Samaria, and was sick: and he sent messengers, and said unto them, Go, enquire of Baalzebub the god of Ekron whether I shall recover of this disease.
3 But the angel of the Lord said to Elijah the Tishbite, Arise, go up to meet the messengers of the king of Samaria, and say unto them, Is it not because there is not a God in Israel, that ye go to enquire of Baalzebub the god of Ekron?
4 Now therefore thus saith the Lord, Thou shalt not come down from that bed on which thou art gone up, but shalt surely die. And Elijah departed.
5 And when the messengers turned back unto him, he said unto them, Why are ye now turned back?
6 And they said unto him, There came a man up to meet us, and said unto us, Go, turn again unto the king that sent you, and say unto him, Thus saith the Lord, Is it not because there is not a God in Israel, that thou sendest to enquire of Baalzebub the god of Ekron? therefore thou shalt not come down from that bed on which thou art gone up, but shalt surely die.
7 And he said unto them, What manner of man was he which came up to meet you, and told you these words?
8 And they answered him, He was an hairy man, and girt with a girdle of leather about his loins. And he said, It is Elijah the Tishbite.
9 Then the king sent unto him a captain of fifty with his fifty. And he went up to him: and, behold, he sat on the top of an hill. And he spake unto him, Thou man of God, the king hath said, Come down.
10 And Elijah answered and said to the captain of fifty, If I be a man of God, then let fire come down from heaven, and consume thee and thy fifty. And there came down fire from heaven, and consumed him and his fifty.
11 Again also he sent unto him another captain of fifty with his fifty. And he answered and said unto him, O man of God, thus hath the king said, Come down quickly.
12 And Elijah answered and said unto them, If I be a man of God, let fire come down from heaven, and consume thee and thy fifty. And the fire of God came down from heaven, and consumed him and his fifty.
13 And he sent again a captain of the third fifty with his fifty. And the third captain of fifty went up, and came and fell on his knees before Elijah, and besought him, and said unto him, O man of God, I pray thee, let my life, and the life of these fifty thy servants, be precious in thy sight.
14 Behold, there came fire down from heaven, and burnt up the two captains of the former fifties with their fifties: therefore let my life now be precious in thy sight.
15 And the angel of the Lord said unto Elijah, Go down with him: be not afraid of him. And he arose, and went down with him unto the king.
16 And he said unto him, Thus saith the Lord, Forasmuch as thou hast sent messengers to enquire of Baalzebub the god of Ekron, is it not because there is no God in Israel to enquire of his word? therefore thou shalt not come down off that bed on which thou art gone up, but shalt surely die.
17 So he died according to the word of the Lord which Elijah had spoken. And Jehoram reigned in his stead in the second year of Jehoram the son of Jehoshaphat king of Judah; because he had no son.
18 Now the rest of the acts of Ahaziah which he did, are they not written in the book of the chronicles of the kings of Israel?
And fire will come out of the witnesses' mouths and destroy their enemies.
Revelation 11:5 King James Version (KJV)
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.
In addition, both Moses and Elijah appeared with Jesus at the Transfiguration, providing some precedence that they could return once again
Matthew 17:3-4 King James Version (KJV)
3 And, behold, there appeared unto them Moses and Elias talking with him.
4 Then answered Peter, and said unto Jesus, Lord, it is good for us to be here: if thou wilt, let us make here three tabernacles; one for thee, and one for Moses, and one for Elias.
What happened to both Elijah and Moses:
2 Kings 2:11 King James Version (KJV)
11 And it came to pass, as they still went on, and talked, that, behold, there appeared a chariot of fire, and horses of fire, and parted them both asunder; and Elijah went up by a whirlwind into heaven.
Jude 9 King James Version (KJV)
9 Yet Michael the archangel, when contending with the devil he disputed about the body of Moses, durst not bring against him a railing accusation, but said, The Lord rebuke thee.
