Revelation 7:11-14
7:11 And all the angels stood there in a circle around the throne and around the elders and the four living creatures, and they threw themselves down with their faces to the ground before the throne and worshiped God,
7:12 saying,
“Amen! Praise and glory,
and wisdom and thanksgiving,
and honor and power and strength
be to our God for ever and ever. Amen!”
7:13 Then one of the elders asked me, “These dressed in long white robes – who are they and where have they come from?”
7:14 So I said to him, “My lord, you know the answer.” Then he said to me, “These are the ones who have come out of the great tribulation. They have washed their robes and made them white in the blood of the Lamb!