Revelation 7:13-15

Then one of the elders answered, saying to me, “Who are these arrayed in white robes, and where did they come from?” 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. Therefore they are before the throne of God, and serve Him day and night in His temple. And He who sits on the throne will dwell among them.