Revelation 7:13 KJV
13 And one of the elders answered, saying unto me, What are these which are arrayed in white robes? and whence came they?
The elder asks John about the multitudes in white robes who stood before the throne. John profess ignorance, then the elder goes on to explain to him who they were.
Revelation 7:14 KJV
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
Why does the elder ask John something he already knew?