The King James and New King James versions translate the "bruising" clauses word for word without making the sense obvious. Other translations render the verb as "wound," "crush," "strike," or "attack." The New International version provides a more descriptive translation: "He will crush your head, and you will strike his heel." The difference is in degree of wounding: Crushing a snake's head destroys it, rendering him powerless, if not dead (see Hebrews 2:14); a snake's strike on the heel, though painful, is minor by comparison.
Another way to look at the comparison focuses on the site of the wounding, the head as compared to the heel. The serpent's wound affects the seat of his intellect and control of his powers, whereas the Seed's wound merely impairs His flesh for a short while - three days and three nights, to be exact.
These bruisings also carry on the theme of humiliation expressed in the preceding verse. The crushing of the serpent's head is understood to be by the heel of the Seed ("He will bruise and tread your head underfoot" - Amplified Bible), so the figure of being "under the heel" of the Messiah is present. This is a common biblical illustration of subservience, submission, and mortification (I Kings 5:3; Lamentations 3:34; Malachi 4:3; Romans 16:20; I Corinthians 15:25; etc.)
Like the symbol of the "Seed," the wounding of the Messiah is another theme that crops up frequently in Scripture. In Numbers 21:8-9, God commands Moses to make a bronze serpent and put it on a pole so "that everyone who is bitten [by the fiery serpents], when he looks at it, shall live." Later, Jesus points to this as a type of His crucifixion, by which He spiritually heals our "serpent bites" (John 3:14-15).
In the Psalms, David writes of the Messiah's wounding: "For You will not leave my soul in Sheol, nor will You allow Your Holy One to see corruption" (Psalm 16:10). Psalm 22 prophesies of Christ's reviling, scourging, and death, showing that, rather than being an end, the Seed's wounding extends God's purpose to every generation! Many other Psalms repeat this theme (Psalm 31:5; 34:20; 41:9-12; 49:15; 69:7-9, 19-21; 109:1-5; etc.).
Isaiah 52:13 - 53:12, the well-known "Suffering Servant" section, contains the very detailed prophecy of Christ's suffering and death. It explains that He, though sinless Himself, endured these ignominious afflictions as a result of our sins. In His wounding, Christ pays the penalty for all sin and qualifies to replace the serpent as ruler over the earth. This, of course, becomes the central theme of the entire New Testament, repeated in some form by nearly every writer.
Richard T. Ritenbaugh
The First Prophecy (Part One)