Revelation 7:9-14
After this I saw a great multitude,
which no one could count,
from every nation, tribe, people, and tongue.
They stood before the throne and before the Lamb,
clothed in white robes with palm branches in their hands,
and crying out in a loud voice:
“Salvation comes from our God, who sits on the throne,and from the Lamb.”

And all the angels stood around the throne
and around the elders and the four living creatures,
and they fell before the throne and worshiped God, saying:
“Amen. Blessing and glory, wisdom and thanksgiving,
honor, power, and mightbe to our God forever and ever. Amen.”

Then one of the elders spoke and said to me,
“Who are these arrayed in white robes,
and from where did they come?”
And I said to him, “Sir, you know.”
And he said to me,
“These are the ones who have come out of the great tribulation
and have washed their robes
and made them white in the Blood of the Lamb.”