Revelation 7:14

So I said to him, "My lord, you know." He said to me, "These are the ones who came out of the great tribulation. They washed their robes, and made them white in the Lamb's blood.

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.