Revelation 7:9, 14

After these things I looked, and behold, a great multitude which no one could number, of all nations, tribes, peoples, and tongues, standing before the throne and before the Lamb, clothed with white robes, with palm branches in their hands

And I said to him, “Sir, you know.” So he said to me, “These are the ones who come out of the great tribulation, and washed their robes and made them white in the blood of the Lamb.