'Robes' in the Bible

After these things I looked, and behold, a great multitude which no one could count, from every nation and all tribes and peoples and tongues, standing before the throne and before the Lamb, clothed in white robes, and palm branches were in their hands;

Then one of the elders answered, saying to me, “These who are clothed in the white robes, who are they, and where have they come from?”

I said to him, “My lord, you know.” And he said to me, “These are the ones who come out of the great tribulation, and they have washed their robes and made them white in the blood of the Lamb.

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