And I will put enmity between you and the woman, and between your seed and her seed; He shall bruise you on the head, and you shall bruise him on the heel."
NASU
                                                                            Genesis 3:15

I will put enmity. The word ('eba) denotes the blood-feud that runs deepest in the heart of man (cf. Num 35:19-20; Ezek 25:15-17; 35:5-6). Thou shalt bruise (shup). A prophecy of a continuing struggle between the descendants of woman and of the serpent to destroy each other. The verb (shup) is rare (cf. Job 9:17; Ps 139:11). It is the same in both clauses. When translated crush, it seems appropriate to the reference concerning the head of the serpent, but not quite so accurate in describing the attack of the serpent on man's heel. It is also rendered (lie in wait for, aim at), or (LXX) (watch for). The Vulgate renders it conteret, "bruise," in the first instance and insidiaberis, "lie in wait," in the other clause. Thus, we have in this famous passage, called the protevangelium, "first gospel," the announcement of a prolonged struggle, perpetual antagonism, wounds on both sides, and eventual victory for the seed of woman. God's promise that the head of the serpent was to be crushed pointed forward to the coming of Messiah and guaranteed victory. This assurance fell upon the ears of God's earliest creatures as a blessed hope of redemption. An unfortunate translation in the Vulgate changes the pronoun his (v. 15 c) from the masculine to the feminine, providing spurious support for unfounded claims concerning "the Blessed Virgin Mary."
(from The Wycliffe Bible Commentary, Electronic Database. Copyright (c) 1962 by Moody Press)