Revelations 7

 In his revelation, John understood the truth saying - 

"...one of the elders answered, saying unto me, What are these which are arrayed in white robes? and whence came they?

14 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.

15 Therefore are they before the throne of God, and serve him day and night in his temple: and he that sitteth on the throne shall dwell among them."  (Revelation 7:13–15)