'It is I' in the Bible

And did He not make you one? Yet the vestige of the Spirit is in him. And what of the one? He was seeking a godly seed. Then guard your spirit, and do not act treacherously with the wife of your youth.

You have said, It is vain to serve God; and, What profit is it that we have kept His charge, and that we have walked as mourners before Jehovah of Hosts?