Revelation 7:13-15

Then one of the elders asked me, “Who are these people in white robes, and where did they come from?” I said to him, “Sir, you know.” Then he told me: These are the ones coming out of the great tribulation. They washed their robes and made them white in the blood of the Lamb. For this reason they are before the throne of God, and they serve him day and night in his temple. The one seated on the throne will shelter them