Revelation 11:3

"And I will give power unto my two witnesses, and they shall prophesy one thousand two hundred and sixty days, clothed in sackcloth."

Revelation 11:2

but the court which is without the temple cast out, and mete it not: for it is given unto the gentiles, and the holy city shall they tread under foot forty two months.

Revelation 12:6

And the woman fled into wilderness, where she had a place, prepared of God, that they should feed her there, one thousand two hundred and sixty days.

Genesis 37:34

And Jacob rent his clothes, and put sackcloth about his loins, and sorrowed for his son a long season.

Numbers 11:26

But there remained two of the men in the host: the one called Eldad, and the other Medad. And the spirit rested upon them for they were of them that were written, but they went not out unto the tabernacle: and they prophesied in the host.

Deuteronomy 17:6

At the mouth of two or three witnesses shall he that is worthy of death, die: but at the mouth of one witness he shall not die.

Deuteronomy 19:15

One witness shall not rise against a man in any manner trespass or sin, whatsoever sin a man sinneth: But at the mouth of two witnesses or of three witnesses shall all matters be tried.

1 Chronicles 21:16

And David lifted up his eyes and saw the angel of the LORD stand between the earth and heaven with a drawn sword in his hand stretched out toward Jerusalem. Then fell David and the elders of Israel, clothed in sack, upon their faces.

Esther 4:1-2

When Mordecai perceived all that was done, he rent his clothes, and put on sackcloth and ashes, and went out into the midst of the city, and cried loud and lamentably,

Job 16:15

I have sewed a sackcloth upon my skin, and lie with my strength in the dust.

Isaiah 22:12

And at the same time shall the LORD of Hosts call men to weeping, mourning, to baldness and a putting on of sackcloth.

Lamentations 2:10

{Yod} The Senators of the daughter Zion sit upon the ground in silence: they have strawed ashes upon their heads, and girded themselves with sackcloth. The maidens of Jerusalem hang down their heads to the ground.

Daniel 12:7

Then heard I the man with the linen clothes, which stood above upon the waters of the flood: when he held up his right and left hand unto heaven, and sware by him which liveth forever, that, "It shall tarry for a time, two times and half a time: when the power of the holy people is clean scattered abroad, then shall all these things be fulfilled."

Matthew 18:16

But if he hear thee not, then take yet with thee one or two, that in the mouth of two or three witnesses, all things may be established.

Luke 24:48

And ye are witnesses of these things.

John 3:5-8

Jesus answered, "Verily, verily I say unto thee: Except that a man be born of water, and of the spirit, he cannot enter into the kingdom of God.

John 3:27

John answered, and said, "A man can receive nothing at all except it be given him from heaven.

John 15:27

And ye shall bear witness also, because ye have been with me from the beginning.

Acts 1:8

but ye shall receive power of the holy ghost which shall come on you. And ye shall be witnesses unto me in Jerusalem, and in all Jewry, and in Samaria, and even unto the world's end."

Acts 2:32

This Jesus hath God raised up, whereof we all are witnesses.

Acts 3:15

and killed the Lord of life whom God hath raised from death, of the which we are witnesses:

Acts 13:31

and he was seen many days of them, which came with him from Galilee to Jerusalem which are his witnesses unto the people.

1 Corinthians 12:28

And God hath also ordained in the congregation, first the apostles, secondarily prophets, thirdly teachers, then them that do miracles; after that, the gifts of healing, helpers, governors, diversity of tongues.

2 Corinthians 13:1

Now come I the third time unto you: "In the mouth of two or three witnesses shall everything stand."

Ephesians 4:11

And the very same, made some Apostles, some Prophets, some Evangelists, some Shepherds, some Teachers:

Revelation 1:5

and from Jesus Christ which is a faithful witness, and first begotten of the dead: and Lord over the kings of the earth. Unto him that loved us and washed us from our sins in his own blood,

Revelation 13:5

And there was a mouth given unto him that spake great things, and blasphemies, and power was given unto him, to continue forty two months.

Revelation 19:10

And I fell at his feet, to worship him. And he said unto me, "See thou do it not. For I am thy fellow servant, and one of thy brethren, and of them that have the testimony of Jesus. Worship God. For the testimony of Jesus is the spirit of prophecy."

Revelation 20:4

And I saw seats, and they sat upon them, and judgment was given unto them: and I saw the souls of them that were beheaded for the witness of Jesus, and for the word of God: which had not worshipped the beast, neither his image, neither had taken his mark upon their foreheads, or on their hands: and they lived, and reigned with Christ a thousand years.

Treasury of Scripture Knowledge

Summary

And I will give power unto my two witnesses, and they shall prophesy a thousand two hundred and threescore days, clothed in sackcloth.

They shall

Bible References

I will give power, etc

John 3:27
John answered, and said, "A man can receive nothing at all except it be given him from heaven.
1 Corinthians 12:28
And God hath also ordained in the congregation, first the apostles, secondarily prophets, thirdly teachers, then them that do miracles; after that, the gifts of healing, helpers, governors, diversity of tongues.
Ephesians 4:11
And the very same, made some Apostles, some Prophets, some Evangelists, some Shepherds, some Teachers:

Witnesses

Revelation 20:4
And I saw seats, and they sat upon them, and judgment was given unto them: and I saw the souls of them that were beheaded for the witness of Jesus, and for the word of God: which had not worshipped the beast, neither his image, neither had taken his mark upon their foreheads, or on their hands: and they lived, and reigned with Christ a thousand years.
Luke 24:48
And ye are witnesses of these things.
John 15:27
And ye shall bear witness also, because ye have been with me from the beginning.
Acts 1:8
but ye shall receive power of the holy ghost which shall come on you. And ye shall be witnesses unto me in Jerusalem, and in all Jewry, and in Samaria, and even unto the world's end."
Acts 2:32
This Jesus hath God raised up, whereof we all are witnesses.
Acts 3:15
and killed the Lord of life whom God hath raised from death, of the which we are witnesses:
Acts 13:31
and he was seen many days of them, which came with him from Galilee to Jerusalem which are his witnesses unto the people.

They shall

Revelation 19:10
And I fell at his feet, to worship him. And he said unto me, "See thou do it not. For I am thy fellow servant, and one of thy brethren, and of them that have the testimony of Jesus. Worship God. For the testimony of Jesus is the spirit of prophecy."

A thousand

Revelation 11:2
but the court which is without the temple cast out, and mete it not: for it is given unto the gentiles, and the holy city shall they tread under foot forty two months.
Revelation 12:6
And the woman fled into wilderness, where she had a place, prepared of God, that they should feed her there, one thousand two hundred and sixty days.

Clothed

Genesis 37:34
And Jacob rent his clothes, and put sackcloth about his loins, and sorrowed for his son a long season.
1 Chronicles 21:16
And David lifted up his eyes and saw the angel of the LORD stand between the earth and heaven with a drawn sword in his hand stretched out toward Jerusalem. Then fell David and the elders of Israel, clothed in sack, upon their faces.
Esther 4:1
When Mordecai perceived all that was done, he rent his clothes, and put on sackcloth and ashes, and went out into the midst of the city, and cried loud and lamentably,
Job 16:15
I have sewed a sackcloth upon my skin, and lie with my strength in the dust.
Isaiah 22:12
And at the same time shall the LORD of Hosts call men to weeping, mourning, to baldness and a putting on of sackcloth.
Lamentations 2:10
{Yod} The Senators of the daughter Zion sit upon the ground in silence: they have strawed ashes upon their heads, and girded themselves with sackcloth. The maidens of Jerusalem hang down their heads to the ground.
John 3:5
Jesus answered, "Verily, verily I say unto thee: Except that a man be born of water, and of the spirit, he cannot enter into the kingdom of God.

General references

Genesis 37:34
And Jacob rent his clothes, and put sackcloth about his loins, and sorrowed for his son a long season.
Numbers 35:30
Whosoever slayeth, shall be slain at the mouth of witnesses. For one witness shall not answer against one person to put him to death.
Romans 9:2
that I have great heaviness, and continual sorrow in my heart.