Christians argue that there are instances in the Hebrew Bible where the word zera is used in a figurative sense, for example:
וְאֵיבָ֣ה ׀ אָשִׁ֗ית בֵּֽינְךָ֙ וּבֵ֣ין הָֽאִשָּׁ֔ה וּבֵ֥ין זַרְעֲךָ֖ וּבֵ֣ין זַרְעָ֑הּ ה֚וּא יְשׁוּפְךָ֣ רֹ֔אשׁ וְאַתָּ֖ה תְּשׁוּפֶ֥נּוּ עָקֵֽב׃ ס
“I will put enmity between you and the woman, and between your offspring and hers; they shall strike at your head, and you shall strike at their heel.” (Genesis 3:15)
Christians contend “the seed of the serpent being those of Eve’s posterity who should imbibe the devil’s spirit and obey the devil’s rule” (Pulpit Commentary). According to Christians, the serpent symbolizes Satan, and his offspring are those human beings who are under his spiritual power.
The problem with this explanation is that it is forced, and the text of Genesis itself doesn’t lend any credence to this view: “Unlike some later Jewish and Christian literature, Genesis does not identify the talking snake with Satan or any other demonic being.” (Jewish Study Bible; p. 16)
In fact, the context of this passage in Genesis is a creation myth regarding the snake: “Now the serpent was the shrewdest of all the wild beasts that the LORD God had made.” (Genesis 3:2)
According to this creation myth, after the serpent had deceived Adam and Eve, God cursed him: “Because you did this, more cursed shall you be than all cattle and all the wild beasts: on your belly shall you crawl and dirt shall you eat all the days of your life” (Genesis 3:15). Apparently, the creation myth of the snake from the book of Genesis would have us believe that prior to the Fall, the serpent was a creature with legs, but due to its wicked behavior, God cursed it by taking away its legs so that it has to crawl on its belly. Interestingly, this creation myth may have some element of scientific truth, since it is widely held that snakes evolved from four-legged reptilian ancestors, perhaps small, burrowing, landbound lizards.
In any case, we clearly see that this passage from Genesis identifies the serpent as an animal, and does not explicitly state that it is a symbol for Satan or any other demonic being. The latter is simply an interpretation of some later Jews and Christians. This is again made more clear when the Verse says: “he [man] shall strike at your head, and you shall strike at his heel”, referencing the fact that humans kill a snake by crushing its head by their feet, while snakes inflict injury and even death upon a human by biting him from under his heel.