Is it considered an oath if a man utters "By God" and then completes the rest of the oath to himself as an inner thought, such as saying "By God, if you don't do such and such, you are divorced"?

Your oath is not binding due to the absence of the element sworn upon, and inner thoughts are not accountable, as the Prophet, peace and blessings be upon him, said: "Indeed, Allah has forgiven my nation for whatever they whisper to themselves, as long as they do not speak of it or act upon it."