'Robes' in the Bible

After these [things] I looked, and behold, a great crowd that no one was able to number, from every nation and tribe and people and language, standing before the throne and before the Lamb, dressed [in] white robes and [with] palm branches in their hands.

And one of the elders answered, saying to me, "These who are dressed [in] the white robes--who are [they], and from where have they come?"

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

Blessed [are] the ones who wash their robes, so that their authority will be over the tree of life and they may enter into the city through the gates.