According to the Koran, Allah taught King David how to make coats of mail (chain mail):
It was We Who taught him the making of coats of mail for your benefit, to guard you from each other’s violence: will ye then be grateful? (Koran 21:80 Yusuf Ali)
We bestowed Grace aforetime on David from ourselves: “O ye Mountains! Sing ye back the Praises of Allah with him! and ye birds (also)! And We made the iron soft for him;- (Commanding), “Make thou coats of mail, balancing well the rings of chain armour, and work ye righteousness; for be sure I see (clearly) all that ye do.” (Koran 34:10-11 Yusuf Ali)
That the Arabic in these two passages denotes chain mail is supported by a number of Muslim commentators:
And We taught him the art of making garments, namely, coats of mail — [which are called labūs] because they are worn (tulbas). He was the first [human being] to make them; hitherto there were [only] plates [of armour] — for you, as well as all mankind, to protect you (read nuhsinakum, [the subject being] ‘God’; or yuhsinakum, [the subject being] ‘David’; or tuhsinakum, [the subject being] ‘garments’) against your [mutual] violence, your wars against your enemies. Will you then, O people of Mecca, be thankful?, for My favours, by believing in the Messenger — in other words, be thankful to Me by [doing] this. (Tafsir al-Jalalayn)
(And We taught him the art of making garments (of mail)) the art of making armours (to protect you in your daring) to protect you from the weapons of your enemy. (Are ye then thankful) of His blessings, which are these armours? (Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs)
And We said: ‘Fashion, from it, long coats of mail — complete suits of armour which the person wearing it drags behind him along the ground — and measure [well] the links’, that is, in the weaving of the coats (the maker of these is called sarrād). In other words, make them so that the rings thereof are arranged properly. And act, O family of David, together with him, righteously. Indeed I am Seer of what you do, and will requite you for it accordingly. (Tafsir al-Jalalayn)
(Saying: Make thou long coats of mail and measure the links (thereof)) the measure of a nail such that it is neither bigger nor smaller than it. (And do ye right) sincerely to Him. (Lo! I am Seer) Aware (of what ye do) of good or evil. (Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs)
Coats of chain armour have to be made with cunning art, if the chains are to fit into each other and the whole garment is to be worn in comfort in fierce warfare. (Abdullah Yusuf Ali 255)
It is not here stated that the making of coats of mail was not known before David. He had to fight many battles against very strong enemies, and there is no doubt that in these battles he had to equip the armies of Israel in the best possible manner. (Maulana Muhammad Ali 659)
Muhammad Asad seems to be in the minority in offering a metaphorical interpretation (555):
The noun labus is synonymous with libas or libs, signifying “a garment” or “garments” (Qamus, Lisan al-Arab). But since this term has occasionally been used by pre-Islamic Arabs in the sense of “mail” or “coats of mail” (ibid.), the classical commentators assume that it has this meaning in the above context as well; and in this they rely on the — otherwise unsupported — statement of the tabi’i Qatadah to the effect that “David was the first to make chain mail” (Tabari). Accordingly, they understand the term ba’s which occurs at the end of the sentence in its secondary sense of “war” or “warlike violence”, and interpret the relevant part of the verse thus: “We taught him how to make coats of mail for you, so that they might fortify you against your [mutual acts of] violence”, or “against [the effects of] you warlike violence”. One should, however, bear in mind that ba’s signifies also “harm”, “misfortune”, “distress”, etc., as well as “danger”; hence it denotes, in its widest sense, anything that causes distress or fear (Taj al-Arus). If we adopt this last meaning, the term labus may be understood in its primary significance of “garment” — in this case the metaphorical “garment of God-consciousness” (libas at-taqwa) of which the Qur’an speaks in 7:26. Rendered in this sense, the above verse expresses the idea that the Almighty taught David how to imbue his followers with that deep God-consciousness which frees men from all spiritual distress and all fears, whether it be fear of one another or the subconscious fear of the Unknown. The concluding rhetorical question, “but are you grateful [for this boon]?” implies that, as a rule, man does not fully realize — and, hence, is not really grateful for — the spiritual bounty thus offered him by God.
The metaphorical interpretation strikes me as less plausible than the literal interpretation, but I mention it in the interest of fairness.
If the literal interpretation is correct, then the Koran is saying chain mail existed in ancient Israel during the reign of King David (ca. 1010-970 BC). In fact, from what I can tell, chain mail was not invented until around the 5th century BC. The case for an historical error in the Koran on this issue may not be definitive but I think it is worth serious consideration.
Ali, Abdullah Yusuf. The Meaning of the Holy Qur’an. CreateSpace, 2010.
Ali, Maulana Muhammad. The Holy Qur’an with English Translation and Commentary. Ahmadiyya Anjuman Isha’at Islam Lahore Inc. U.S.A., 2002.
Asad, Muhammad. The Message of the Qur’an. Second edition. The Book Foundation, 2008.