15. thy seed--not only evil spirits, but wicked men.
      seed of the woman--the Messiah, or His Church [CALVIN, HENGSTENBERG].
      I will put enmity between thee and the woman--God can only be said to do so by leaving "the serpent and his seed to the influence of their own corruption; and by those measures which, pursued for the salvation of men, fill Satan and his angels with envy and rage."
      thou shalt bruise his heel--The serpent wounds the heel that crushes him; and so Satan would be permitted to afflict the humanity of Christ and bring suffering and persecution on His people.
      it shall bruise thy head--The serpent's poison is lodged in its head; and a bruise on that part is fatal. Thus, fatal shall be the stroke which Satan shall receive from Christ, though it is probable he did not at first understand the nature and extent of his doom.

JFB.