The serpent is used to show attachment. The reason a snake is chosen is because this is a poisonous animal that is fully attached to the ground. The serpent is a metaphor for being attached to possessions, manmade ideals and how dangerous and poisonous to the spirit such a state is.
The woman is the Law and religion of God. Enmity between the woman and the serpent means that every new religion of God is faced with the entrenched, corrupted religion that will do everything to kill or prevent the Law of God, or the new religion of God from taking root.
We have seen this with Jesus who was murdered along with countless souls killed for their love of Christ. We have seen it in Islam when the family of Muhammad were systematically killed if they in any way rose to prominence, because it was prophesied that the next prophet would be a descendant of Muhammad and He was.
In the case of Baha'u'llah and the Bab, tens-of-thousands were killed, the Bab was executed and Baha'u'llah spent 49 years imprisoned.
The serpent is the corrupted human ego, the woman is the Law of God born of a new religion and enmity leads to the death and imprisonment of the Teachers of God down through the ages.
