Revelation 7:14

And I said to him, Sir, you know. And he said to me, These are they who have come out of much tribulation, and have washed their robes, and made them white in the blood of the Lamb:

1 John 1:7

But if we walk in the light, as he is in the light; we have fellowship with one another, and the blood of Jesus Christ the Son cleanses us from all sin.

Revelation 1:5

and from Jesus Christ, the faithful witness, the first born of the dead, and the ruler of the kings of the earth; to him who has loved us, and washed us from our sins in his own blood,

Revelation 22:14

(Happy are they who keep his commandments, that they may have the privilege to eat of the tree of life; and they shall enter by the gates into the city.

1 Peter 1:19

but with the precious blood of Christ, as of a lamb without blemish, and without spot;

Revelation 2:9

I know your works, and tribulation, and poverty, (but you are rich,) and I know the slander of those who say they are Jews, and are not; but are the assembly of Satan.

Revelation 5:9

And they sung a new song, saying, Worthy art thou to take the scroll, and to open the seals of it; for thou wast slain, and hast redeemed us to God by thy blood, out of every tribe, and language, and people, and nation;

Revelation 6:9-11

And when he opened the fifth sea, I saw, under the altar, the souls of those who were slaughtered on account of the word of God, and the testimony which they held.

Revelation 12:11

And they have overcome him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives to the death.

Revelation 15:2

And I saw, as it were, a sea of glass mingled with fire; and those who overcame the beast, and its image, and its mark, and the number of its name; standing by the sea of glass, having the harps of God.

Revelation 17:6

And I saw the woman drunk with the blood of the saints, and with the blood of the martyrs of Jesus: and when I saw her, I wondered with great amazement.

Treasury of Scripture Knowledge

Summary

And I said unto him, Sir, thou knowest. And he said to me, These are they which came out of great tribulation, and have washed their robes, and made them white in the blood of the Lamb.

Bible References

And have

Revelation 1:5
and from Jesus Christ, the faithful witness, the first born of the dead, and the ruler of the kings of the earth; to him who has loved us, and washed us from our sins in his own blood,
1 John 1:7
But if we walk in the light, as he is in the light; we have fellowship with one another, and the blood of Jesus Christ the Son cleanses us from all sin.

The blood

Revelation 5:9
And they sung a new song, saying, Worthy art thou to take the scroll, and to open the seals of it; for thou wast slain, and hast redeemed us to God by thy blood, out of every tribe, and language, and people, and nation;
Revelation 12:11
And they have overcome him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives to the death.
1 Peter 1:19
but with the precious blood of Christ, as of a lamb without blemish, and without spot;