Revelation 7: 2 - 4, 9 - 14
2 Then I saw another angel ascend from the rising of the sun, with the seal of the living God, and he called with a loud voice to the four angels who had been given power to harm earth and sea,
3 saying, "Do not harm the earth or the sea or the trees, till we have sealed the servants of our God upon their foreheads."
4 And I heard the number of the sealed, a hundred and forty-four thousand sealed, out of every tribe of the sons of Israel,
9 After this I looked, and behold, a great multitude which no man could number, from every nation, from all tribes and peoples and tongues, standing before the throne and before the Lamb, clothed in white robes, with palm branches in their hands,
10 and crying out with a loud voice, "Salvation belongs to our God who sits upon the throne, and to the Lamb!"
11 And all the angels stood round the throne and round the elders and the four living creatures, and they fell on their faces before the throne and worshiped God,
12 saying, "Amen! Blessing and glory and wisdom and thanksgiving and honor and power and might be to our God for ever and ever! Amen."
13 Then one of the elders addressed me, saying, "Who are these, clothed in white robes, and whence have they come?"
14 I said to him, "Sir, you know." And he said to me, "These are they who have come out of the great tribulation; they have washed their robes and made them white in the blood of the Lamb.

EWTN