'Clothed in White' in the Bible

He that overcometh, this man shall be clothed in white robes; and I will in no wise blot his name out of the book of life, and I will confess his name before my Father, and before his angels.

And around the throne were twenty-four thrones; and upon these thrones I saw twenty-four presbyters seated, clothed in white robes; and they had on their heads golden crowns.

After these things I looked, and beheld a great multitude, which no man could number, out of every nation, and tribe, and people, and tongue, standing before the throne, and before the Lamb, clothed in white robes, and palm branches in their hands

And one of the presbyters addressed me, saying, Who are these persons who are clothed in white robes? and from whence came they?