“declares me righteous.” The Hebrew word is tsadaq (#06663 צָדַק ), and here in Isaiah 50:8 it is in the Hiphel aspect of the verb, and can mean to give one justice or bring justice to someone; to acknowledge or declare that someone is right, righteous, or not guilty; to pronounce someone, or treat someone, as not guilty (innocent); or to help someone gain his rights. Here in Isaiah 50:8, in the context of the coming Messiah who was accused of being a criminal, tsadaq carries a couple of those meanings. God would declare (and prove) that Jesus was righteous by raising him from the dead, and He would help Jesus gain his rights by making him Lord and giving him all authority in heaven and on earth. It is impossible to bring all that into English without writing a greatly expanded translation, and so most English translations choose either “justify” or “vindicate” as a translation. The REV went with “declares me righteous” because the person who is declared righteous in the sight of God will then get whatever they rightly deserve as well, and it connects the righteous Messiah with all the other righteous people in the Bible.