Let me quote myself instead of retyping everything:
" First, I recommend that you all start using biblegateway.com In there, you can put the passage in question and then you can click (just below the translation) on " Genesis 3.15 in all English translations." It will then list almost, if not all, English translations and revisions in existence. It's astonishing that people heavily continue to use the KJV and its editions and revisions, and barely mention or reference more up-to-date and more reliable translations such as the ESV, ISV, NET and LEB.
Second, I recommend that you all start taking advantage of the NET Bible and its translation notes. Yes, the NET Bible is free online and it includes translation notes by the translators. It's not flawless, but it's scholarly and extremely useful. "
In biblegateway.com, the only English translation that translates "heel" in the plural is the CEB (Common English Bible, 2011). None of the translations are wrong. There are a variety of translation methodologies and philosophies. So, some people that have never done biblical translation (a bit different than modern translation work in modern languages) will often erroneously accuse translations of mistranslation where it sometimes does not apply ( Im not denying that this never happens! Of course, it does ). Let's be careful -- Im not accusing Newman of this -- not to jump to conclusions and accuse translators of mistranslating.
In this case, the passage in question refers to the woman's descendants (humanity--and only remotely: Israel, David, Christ) and the serpent's descendants (anyone in line with Satan and the enemies of Israel and God--not a biological genealogy). But, the Hebrew text uses the singular which immediately refers to the woman's offspring (collective singular) and the serpent's offspring (collective singular). Therefore, the Hebrew text's "head" and "heel" are also singular, but evidently referring to many individuals and groups of beings on both sides. Therefore, again, a collective singular.
It's not completely wrong, then, to translate with a plural. But, translating with a plural means translating not only the text, but the meaning of the text.
Here are the NET Bible translator notes, which align somewhat with what critical commentaries and Hebrew scholars have said in the past:
On "hostility" in Gen 3.15
tn The Hebrew word translated “hostility” is derived from the root
אֵיב (’ev, “to be hostile, to be an adversary [or enemy]”). The curse
announces that there will be continuing hostility between the serpent
and the woman. The serpent will now live in a “battle zone,” as it
were.
Biblical Studies Press, The NET Bible First Edition; Bible. English.
NET Bible.; The NET Bible (Biblical Studies Press, 2005).
On "offspring" in Gen 3.15
sn The Hebrew word translated “offspring” is a collective singular.
The text anticipates the ongoing struggle between human beings (the
woman’s offspring) and deadly poisonous snakes (the serpent’s
offspring). An ancient Jewish interpretation of the passage states:
“He made the serpent, cause of the deceit, press the earth with belly
and flank, having bitterly driven him out. He aroused a dire enmity
between them. The one guards his head to save it, the other his heel,
for death is at hand in the proximity of men and malignant poisonous
snakes.” See Sib. Or. 1:59–64. For a similar interpretation see
Josephus, Ant. 1.1.4 (1.50–51).
Biblical Studies Press, The NET Bible First Edition; Bible. English.
NET Bible.; The NET Bible (Biblical Studies Press, 2005).
On "attack" in Gen 3.15
tn Heb “he will attack [or “bruise”] you [on] the head.” The singular
pronoun and verb agree grammatically with the collective singular noun
“offspring.” For other examples of singular verb and pronominal forms
being used with the collective singular “offspring,” see Gen 16:10;
22:17; 24:60. The word “head” is an adverbial accusative, locating the
blow. A crushing blow to the head would be potentially fatal.
Biblical Studies Press, The NET Bible First Edition; Bible. English.
NET Bible.; The NET Bible (Biblical Studies Press, 2005).
On "you" in Gen 3.15
sn You will attack her offspring’s heel. Though the conflict will
actually involve the serpent’s offspring (snakes) and the woman’s
offspring (human beings), v. 15b for rhetorical effect depicts the
conflict as being between the serpent and the woman’s offspring, as if
the serpent will outlive the woman. The statement is personalized for
the sake of the addressee (the serpent) and reflects the ancient
Semitic concept of corporate solidarity, which emphasizes the close
relationship between a progenitor and his offspring. Note Gen 28:14,
where the LORD says to Jacob, “Your offspring will be like the dust of
the earth, and you [second masculine singular] will spread out in all
directions.” Jacob will “spread out” in all directions through his
offspring, but the text states the matter as if this will happen to
him personally.
Biblical Studies Press, The NET Bible First Edition; Bible. English.
NET Bible.; The NET Bible (Biblical Studies Press, 2005).
On "heel" in Gen 3.15
as an explanation for the hostility between snakes and humans. (In the
broader ancient Near Eastern context, compare the Mesopotamian serpent
omens. See H. W. F. Saggs, The Greatness That Was Babylon, 309.) This
ongoing struggle, when interpreted in light of v. 15, is a tangible
reminder of the conflict introduced into the world by the first
humans’ rebellion against God. Many Christian theologians (going back
to Irenaeus) understand v. 15 as the so-called protevangelium,
supposedly prophesying Christ’s victory over Satan (see W. Witfall,
“Genesis 3:15—a Protevangelium?” CBQ 36 [1974]: 361–65; and R. A.
Martin, “The Earliest Messianic Interpretation of Genesis 3:15,” JBL
84 [1965]: 425–27). In this allegorical approach, the woman’s
offspring is initially Cain, then the whole human race, and ultimately
Jesus Christ, the offspring (Heb “seed”) of the woman (see Gal 4:4).
The offspring of the serpent includes the evil powers and demons of
the spirit world, as well as those humans who are in the kingdom of
darkness (see John 8:44). According to this view, the passage gives
the first hint of the gospel. Satan delivers a crippling blow to the
Seed of the woman (Jesus), who in turn delivers a fatal blow to the
Serpent (first defeating him through the death and resurrection [1 Cor
15:55–57] and then destroying him in the judgment [Rev 12:7–9;
20:7–10]). However, the grammatical structure of Gen 3:15b does not
suggest this view. The repetition of the verb “attack,” as well as the
word order, suggests mutual hostility is being depicted, not the
defeat of the serpent. If the serpent’s defeat were being portrayed,
it is odd that the alleged description of his death comes first in the
sentence. If he has already been crushed by the woman’s “Seed,” how
can he bruise his heel? To sustain the allegorical view, v. 15b must
be translated in one of the following ways: “he will crush your head,
even though you attack his heel” (in which case the second clause is
concessive) or “he will crush your head as you attack his heel” (the
clauses, both of which place the subject before the verb, may indicate
synchronic action).
Biblical Studies Press, The NET Bible First Edition; Bible. English.
NET Bible.; The NET Bible (Biblical Studies Press, 2005).
LET ME ADD MY CONVERSATION WITH HOWARD FOR CLARITY--UPDATE MARCH 5 2019
Some have doubted the "collective singular". It's in three specialized resources I have:
Christo Van der Merwe et al., A Biblical Hebrew Reference Grammar
(electronic ed.; Sheffield: Sheffield Academic Press, 1999)
Frederic Clarke Putnam, Hebrew Bible Insert: A Student’s Guide to the
Syntax of Biblical Hebrew (Quakertown, PA: Stylus Publishing, 2002)
James Swanson, Dictionary of Biblical Languages with Semantic Domains
: Hebrew (Old Testament) (Oak Harbor: Logos Research Systems, Inc.,
1997)
It's also in the Lexham Interlinear produced by the same grammarian who produced BHRG (1999).
Christo van der Merwe, The Lexham Hebrew-English Interlinear Bible
(Bellingham, WA: Lexham Press, 2004
For examples other than Gen 3.15, look at the comments below.
Now, Im not saying I prefer the Swedish translation nor am I saying that they respect some sort of grammar rule--they did not. In other words, the Swedish translators seem to have translated the meaning of the literal Hebrew text. That is, their translation reflects an interpretation of the collective singular nouns. So, it's not completely wrong, but I do not prefer it. It's preferable to translate what it is and have Bible footnotes to explain what it might actually mean. This is why I like the NET Bible translator notes. It's not flawless, but it's excellent.
In Gen 3.15, the Hebrew text reads "... her offspring " and then becomes "he". In other words, what is the antecedent of "He will bruise your head"? The antecedent of "He" is not the woman, but her offspring. Therefore, the woman's offspring = He, and He will bruise the serpent's head and the serpent will bruise his heel. So, again : Woman's OFFSPRING = HE = HEEL.
It works in Hebrew and English because the woman represents the mother of humanity. Her offspring might represent (must be interpreted) the chosen/good generation that will come out of her = Israel + kings + Messiah--however we interpret it. Also, note that the seed of the serpent is not necessarily biological descent. Therefore, there isn't necessarily a one-to-one correspondence between the woman's seed and the serpent's seed. So, it doesn't matter what happens to the feminine. The woman's offspring or seed represents other people other than her own self, and so can be represented as a "he". As I said in my initial answer above, the Swedish translation translated the text by interpreting the literal text "he" --> "they" | "heel" --> "heels".