The Odyssey 5.182–191

and the down-flowing water of the Styx, which is the greatest and most dread oath for the blessed gods, that I will not plot against thee any fresh mischief to thy hurt. Nay, I have such thoughts in mind, and will give such counsel, as I should devise for mine own self, if such need should come on me. For I too have a mind that is righteous, and the heart in this breast of mine is not of iron, but hath compassion.”