Generally, Christians believe that the two witnesses are Enoch and Elijah as these two were taken to heaven alive.
In the book of (Zachariah 4:2-3,14) we read about two anointed people.
And said unto me, what seest thou? And I said, I have looked, and behold a candlestick all of gold, with a bowl upon the top of it, and his seven lamps thereon, and seven pipes to the seven lamps, which are upon the top thereof: And two olive trees by it, one upon the right side of the bowl, and the other upon the left side thereof.
Then said he, these are the two anointed ones that stand by the Lord of the whole earth.
In the book of Revelation 11:3-4)
And I will give power unto my two witnesses, and they shall prophesy a thousand two hundred and threescore days, clothed in sackcloth.
These are the two olive trees, and the two candlesticks standing before the God of the earth.
So in both the books we read that these two witnesses are anointed people of God.
We read about Enoch in the book of Genesis, Hebrews and Jude.
And Enoch walked with God: and he was not; for God took him. (Gen.5:24)
By faith Enoch was translated that he should not see death; and was not found, because God had translated him: for before his translation he had this testimony, that he pleased God. (Heb.11:5)
And Enoch also, the seventh from Adam, prophesied of these, saying, Behold, the Lord cometh with ten thousand of his saints, To execute judgment upon all, and to convince all that are ungodly among them of all their ungodly deeds which they have ungodly committed, and of all their hard speeches which ungodly sinners have spoken against him. (Jude:14,15)
So we understand that Enoch walked with God, Pleased God and prophesied about the judgment of God. So he might have been anointed by God as a prophet.
But nowhere was it mentioned that he will come back to the earth. But because he did not die, he has to come to earth to die as it is written that it is appointed unto men once to die but after this the judgment. (Heb.9:27)
Now let us study about Elijah. Elijah was a prophet during the period of Ahab the king of Israel. He was called as Elijah the Tishbite and he belong to Gilead. (I King 1:17) He was taken to heaven alive (II Kings 2:11)
Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the LORD:
And he shall turn the heart of the fathers to the children, and the heart of the children to their fathers, lest I come and smite the earth with a curse. (Malachi 4:5-6)
The voice of him that crieth in the wilderness, prepare ye the way of the LORD, make straight in the desert a highway for our God. (Isaiah 40:3)
But regarding Elijah Jesus Crist Himself told that Elijah has already come. (Matt. 11:14, Matt. 17:12) (Mk.9:12,)
For all the prophets and the law prophesied until John.
Verily I say unto you, among them that are born of women there hath not risen a greater than John the Baptist: notwithstanding he that is least in the kingdom of heaven is greater than he.
And if ye will receive it, this is Elias, which was for to come.
He that hath ears to hear, let him hear. (Matt.11:11,14-15)
And Jesus answered and said unto them, Elias truly shall first come, and restore all things.
But I say unto you, That Elias is come already, and they knew him not, but have done unto him whatsoever they listed. Likewise, shall also the Son of man suffer of them.
Then the disciples understood that he spake unto them of John the Baptist.
And he answered and told them, Elias verily cometh first, and restoreth all things; and how it is written of the Son of man, that he must suffer many things, and be set at nought.
But I say unto you, That Elias is indeed come, and they have done unto him whatsoever they listed, as it is written of him. (Mk.9:12,13)
So let us conclude that one among the two witnesses are not Elijah. Then who is he?
Now let us study about John the apostle.
In (John 21:17) Jesus said that John will tarry till He come back.
Then Peter, turning about, seeth the disciple whom Jesus loved following; which also leaned on his breast at supper, and said, Lord, which is he that betrayeth thee?
Peter seeing him saith to Jesus, Lord, and what shall this man do?
Jesus saith unto him, If I will that he tarries till I come, what is that to thee? follow thou me.
Then went this saying abroad among the brethren, that that disciple should not die: yet Jesus said not unto him, He shall not die; but, If I will that he tarries till I come, what is that to thee? (Jn.21:20-23)
Also Jesus said in three gospels that till He comes back there will be some (more than one, perhaps two or more) will not die and others will die.
Verily I say unto you, there be some standing here, which shall not taste of death, till they see the Son of man coming in his kingdom. (Matt,16:28)
And he said unto them, Verily I say unto you, that there be some of them that stand here, which shall not taste of death, till they have seen the kingdom of God come with power. (Mk.9:1)
Some saints of God interpret this verse as kingdom of God coming with power is nothing but the Day of Pentecost, and the power of God came upon the 120 disciple and they all received the Holy Ghost and talked in many languages. But it is incorrect because on that day all the disciples except Judas Iscariot were alive. But the verse says that only few will be alive means that the remaining all would be dead.
But I tell you of a truth, there be some standing here, which shall not taste of death, till they see the kingdom of God. (Lk.9:27)
From these verses we conclude that John the apostle is one among them who shall not die till Jesus come back.
One may think is it possible for a man to live more than two thousand years? Yes, it is possible. Jesus said to Martha it is possible not to die.
And whosoever liveth and believeth in me shall never die. Believest thou this? (Jn.11:26)
Also in the book of Sadhu Sundar Singh, chapter 6, he mentioned about a maharishi who is one among the many who live in caves of snow peaked mount Kailash in the range of Himalayas.
He met him in the years 1912, 1916 and 1917 and at that time he said his age was 300 years and God asked him to be in that place and pray for the saints live in the world. So now his age is 400 years. He is from Alexandria of Egypt and reading a leather bound Bible written in Greek.
So Apostle John and one more disciple with him might be living like wise. They are anointed saints of God.
Also in (Rev.10:1,2,3,8-11) Here a mission of prophesying is given to St. John from God and through a powerful angel. This mission was not carried out by St. John as he was out law in the Roman Govt. and that prophecy was not for that period, and he is expected to accomplish it prior to Christ’s secret coming as per (Rev.11:2-4) and the temple of God would be there.
The particulars of the other disciple are not given to us. Jesus loved two disciples more, they were John the Divine and Nathanael in whom Jesus did not find any guile. This Nathanael accompanied Peter when he went for fishing after the death and resurrection of Christ. So Nathanael may be the other witness accompanying John. Enoch may come to prophecy or may not.
Jesus saw Nathanael coming to him, and saith of him, behold an Israelite indeed, in whom is no guile!(John 1:47)
If John the Divine has to come to prophecy, as Jesus said, he will tarry till Jesus comes back, let us match it with the word of God.
During the sixth trumpet, two woes are taking place. 1. Army of the horses and horse men numbering 20 crore. (Rev.9:13-21) 2. Two witnesses torment the people of the earth who resist them and did not allow them to prophecy. Even after their death, when they resurrect without burial, after 3 ½ days a great earth quake takes place and heavy loss of lives and property takes place and the second woe is past. (Rev.11:13,14) When they ascend to heaven the Seventh angel blows the trumpet and the Mystery of God is taking place and the Bridal Church or the Man child is raptured.
The second woe is past; and, behold, the third woe cometh quickly.
And the seventh angel sounded; and there were great voices in heaven, saying, the kingdoms of this world are become the kingdoms of our Lord, and of his Christ; and he shall reign for ever and ever. (Rev. 11:14,15)
Here we find that John the Divine was alive and tarried till the Seventh Trumpet or the Secret Coming of Christ for His Bride, but for 3 ½ days. At his resurrection without burial, Christ returns and John the Divine could see Jesus Christ coming in His Kingdom! John’s apostolic companion also might be with him. Here the Word (Matt.16:28) is fulfilled.
Verily I say unto you, there be some standing here, which shall not taste of death, till they see the Son of man coming in his kingdom. (Matt. 16:28)
Also let us study about the unique nature of John the divine.
John the apostle or John the Divine has great virtue which other apostles lack. It is written that they quarreled among themselves that who was great among themselves?
But this John had a hidden life in the Lord. In his gospel of St. John, he has not referred about him a single word up to 12 chapters among his 21 chapters. In the 13th chapter he mentioned about him not by his name but as one of His disciples whom Jesus loved.
Now there was leaning on Jesus’ bosom one of his disciples, whom Jesus loved. (Jn.13:23)
Again he refers in (Jn. 18:15) Here, he refers him as another disciple.
And Simon Peter followed Jesus, and so did another disciple: that disciple was known unto the high priest, and went in with Jesus into the palace of the high priest. (Jn.18:15)
Then in (Jn. 19:26) he refers about him as disciple whom Jesus loved.
When Jesus therefore saw his mother, and the disciple standing by, whom he loved, he saith unto his mother, Woman, behold thy son!
The disciple who stood near the cross and received the mother of Jesus as his own mother, will he not be available for the burial. He was there, but hided himself, and exposed Joseph and Nicodemus.
And after this Joseph of Arimathaea, being a disciple of Jesus, but secretly for fear of the Jews, besought Pilate that he might take away the body of Jesus: and Pilate gave him leave. He came therefore, and took the body of Jesus.
And there came also Nicodemus, which at the first came to Jesus by night, and brought a mixture of myrrh and aloes, about a hundred-pound weight.
Then took they the body of Jesus, and wound it in linen clothes with the spices, as the manner of the Jews is to bury. (Jn.19:38-40)
Then he revealed him in (Jn.20:4) as other disciple.
So they ran both together: and the other disciple did outrun Peter, and came first to the sepulture. (Jn. 20:4)
Then he refers about him in (Jn.21:7,20) as disciple whom Jesus loved.
Therefore, that disciple whom Jesus loved saith unto Peter, it is the Lord. Now when Simon Peter heard that it was the Lord, he girts his fisher’s coat unto him, (for he was naked,) and did cast himself into the sea. (Jn.21:7)
We find in Bible that St. Matthew referred John the apostle 3 times, St. Mark referred 10 times, St. Luke referred 7 times and John referred nil time.
So the Lord Jesus said to Peter about John, If I will that he (John) tarry till I come, what is that to thee? (Peter) follow thou me. (Jn. 21:22) Hence that disciple John did not die and tarries till Jesus comes back.