'Robes' in the Bible

After these things I saw, and behold, a great multitude, which no man could number, out of every nation and of all tribes and peoples and tongues, standing before the throne and before the Lamb, arrayed in white robes, and palms in their hands;

And one of the elders answered, saying unto me, These that are arrayed in white robes, who are they, and whence came they?

And I say unto him, My lord, thou knowest. And he said to me, These are they that come of the great tribulation, and they washed their robes, and made them white in the blood of the Lamb.

Blessed are they that wash their robes, that they may have the right to come to the tree of life, and may enter in by the gates into the city.