Revelation 7:9-14

After this I looked, and there before me was a great multitude that no one could count, from every nation, tribe, people and language, standing before the throne and before the Lamb. They were wearing white robes and were holding palm branches in their hands. And they cried out in a loud voice: “Salvation belongs to our God, who sits on the throne, and to the Lamb.” All the angels were standing around the throne and around the elders and the four living creatures. They fell down on their faces before the throne and worshiped God, saying: “Amen! Praise and glory and wisdom and thanks and honor and power and strength be to our God for ever and ever. Amen!” Then one of the elders asked me, “These in white robes—who are they, and where did they come from?” I answered, “Sir, you know.” And he said, “These are they who have come out of the great tribulation; they have washed their robes and made them white in the blood of the Lamb.