Revelation 7:9, 13-14

After this I looked, and behold, right in front of me I saw a vast multitude of people—an enormous multitude so huge that no one could count—made up of victorious ones from every nation, tribe, people group, and language. They were all in glistening white robes, standing before the throne and before the Lamb with palm branches in their hands.

Then one of the elders asked me, “Who are these in glistening white robes, and where have they come from?” I answered, “My lord—you must know.” Then he said to me, “They are ones who have washed their robes and made them white in the blood of the Lamb and have emerged from the midst of great pressure and ordeal.