'The heel,' as mentioned in Genesis 3:15, signifies the literal sense of the Word.

'To lift up the heel the against the Lord,' as mentioned in Psalm 41:10, signifies to pervert the literal sense of the Word even unto the negation of the Lord, and to the falsification of every truth. Since the Word is divine truth, therefore, also this is in image before the Lord as a divine man. Its ultimate sense corresponds to the heel, and as this was perverted by the Jews by application thereof to their false traditions, therefore, this is signified by lifting up the heel against the Lord. 'The heel' signifies natural things of the lowest order.

'The heel which the serpent should bruise,' as mentioned in Genesis 3:15, signifies the lowest natural principle, or the body.

(References: Arcana Coelestia 259, 2162, 3304)