Genesis 3:14 - The Popular Commentary by Paul E. Kretzmann

And the Lord God said unto the serpent, Because thou hast done this, thou art cursed above all cattle and above every beast of the field; upon thy belly shalt thou go, and dust shalt thou eat all the days of thy life. The serpent, which had placed its cunning into the service of the devil, was the first to receive its sentence, and with it Satan, who had hid himself in this form for the purpose of seducing man. The punishment which struck the reptile was only a type of the devil's punishment. The serpent's form and means of locomotion were changed in this curse which singled it out from all animals, both those that were eventually domesticated and those that would remain game and predatory animals of the field. Instead of walking upright, the serpent was hereafter to wind itself along in the dust, which it could, incidentally, not avoid swallowing.