Revelation 7:9, 13

After these things I looked, and behold, a great multitude which no one could count, from every nation and all tribes and peoples and tongues, standing before the throne and before the Lamb, clothed in white robes, and palm branches were in their hands

Then one of the elders answered, saying to me, “These who are clothed in the white robes, who are they, and where have they come from?”