The bible is quite specific. Leviticus 19:19 says “You are to keep My statutes. You shall not breed together two kinds of your cattle; you shall not sow your field with two kinds of seed, nor wear a garment upon you of two kinds of material mixed together.”
Also, Deuteronomy 22:11 says it again: “You shall not wear a material mixed of wool and linen together.”
Seems a strange prohibition, why was it forbidden to mix fabrics?
I was told that the priestly ceremonial outfits were a wool/linen combo, and the prohibition was basically, “let the religious clothes be the fanciest clothes”.
It is part of the purity code of the OT. The idea is that it is dangerous to cross boundaries.
It may be related to the commandment that the Jews not mix with other people. See Nehemiah 13:1-3, 23-27.
Regards,
Shodan
The traditional rabbinical answer is “we follow the Law because God says so”.
Of course, not everyone stops there, and a number of scholars go on to ask why God says so. One possible explanation is that different fibers will shrink at different rates, and so mixing fibers in a single garment, if not done correctly, can result in the whole thing pulling apart and wearing out quickly.
Another common explanation, and one which can apply to most of the Laws, is that it served simply as a tribal identifier: We do things differently from those people over there because we’re not those people over there, and we wish to remain separate.
So blends were considered tacky, even in biblical times?
He can be pretty proactive; think it as his attempt to keep people who really shouldn’t from wearing pants with “just a hint of Spandex”.
It is based on the notion of purity. Admixtures were considered “impure”, generally speaking. That went for cattle, fields or garments.
I’m not convinced it had any practical purpose. To my mind, it was just obvious to the redactors of the OT that “pure” things were better, and so more pleasing to God, than “impure” things.
Impossible to determine. The closest we can get is “The prophets Jeremiah and Ezekiel wrote: this is what God says.”
So the minds of the prophets became the mind of God. Crazy, insane prophets were no exception. What the prophets’ schizophrenic minds dreamed up became The Law.
isn’t that where “kosher” originated from ?
This could just be a simple matter of cotton cloth is better in summer, wool is better in winter and mixing the two makes the cloth worthless … clothing was expensive back then, and these weren’t a particularly wealthy people who were wandering the desert 40 years lost.
Picking up food that falls from the sky … yeech … not a wealthy people a’tall.
My speculation was that it was intended as a metaphorical warning against the possibility of assimilation. The Jews were a numerically small people surrounded by much larger cultures. The risks of conquest were obvious. But the threat of Jewish culture being lost through friendly relations with neighboring cultures was also real. If Jews started mixing in with the cultures of these countries, their distinct identity would be lost and they would essentially become Persians or Egyptians or Greeks. Leviticus 19:19 was a reminder that while they could peacefully live alongside other people, they should always maintain their own separate culture and not mix in with the majority culture.
I don’t think so, and here’s my reasoning: the redactors of the OT had no problems with coming right out and saying that the Hebrews should not take up the habits of foreign folks, so there is no reason they would have bothered with metaphorical circumlocutions on the topic.
Rather, I think it is just a matter of ritual purity, like keeping kosher by not mixing milk and meat. Culturally, the redactors of the OT apparently simply found mixing things to be “impure” and thus bad. I don’t think it goes any deeper than that.
The previous chapter, for example, dealt with matters of sexual immorality - and similarly, I would say it was just culturally obvious to the redactors that having sex with close relatives or animals was bad; they indeed contrast that with what foreigners do, but not because they feared Israelites would become foreigners, or to create some symbolic distinction between Israelites and foreigners, but rather because God would punish them if they took up such immoral practices.
It was also a dig at the foreigners - the suggestion being that foreigners went around having sex with animals or their parents all the time suited Israelite prejudices, as well as justifying taking over from said foreigners.
Leviticus 18:24
I once had a rabbi tell me that mixing different fabrics implies that God didn’t make enough of them. If you need a blend, it means the originals are not sufficient, and you are basically one upping God.
As a Conservadox Jew, this is what I was going to say. Why keep kosher? Why put fringes on our garments? G-d said so. We can ask if there is a humanly fathomable purpose as to WHY G-d said so. But that’s irrelevant.
As for it being a tribal identifier, that is indeed a common explanation.
Malthus I don’t see why the redactors couldn’t say it bluntly in one place, and obliquely in another. They kept both versions of creation.
That’s a different issue, though. They kept two versions of the creation myth most likely because one was current in the Northern Kingdom and one was current in the Southern, and they didn’t want to piss either off (or at least, that’s a plausible explanation I’ve heard), but I see little evidence that the redactors were concerned about making purely metaphorical statements when it came to such matters as not taking up foreign ways - they could not be more explicit on that point.
As for a “tribal identifier” - that may work with the clothes you wear, but it makes little sense with the fields you sew or the animals you breed. While strangers may notice right away what clothes you wear, they are unlikely to check to see what you are planting in your fields. Yet all three are linked in the same verse.
In any event, it is a remarkably subtle “identifier”. Simply making one’s clothes out of one sort of fabric is something lots of people do anyway, and is likely to be difficult to detect without minute inspection of the clothes in question. It lacks the obvious drama of, say, circumcision.
To my mind, both explanations - metaphorical statement concerning separation or tribal identifier - are simply over-thinking the matter.
I’m certainly not an OT scholar, but a quick GoodSearch brought up 7 mentions of mules in the OT, with some distinguished folks astride them. Even a city feller like me knows that mules are an admixture of horses and donkeys, and that seemed to be okay with the Jews.
http://www.artbible.info/concordance/m/9229-1.html
The basic answer is, “we don’t know, it’s just one of those things that G-d says to do.”
There is Midrashic speculation that it is related to Cain and Abel - Cain’s sacrifice was flax plants (this is from oral tradition), Abel’s was sheep (that’s explicit in the Bible), and since one brother killed the other, it’s wrong to mix the two.
AskNott: By Jewish law, Jews are not allowed to breed horses and donkeys together, but it is not forbidden to make use of a mule if a non-Jew had created one (or it was conceived in the wild).
Accusing the “others” of sexual deviancy as well *as sexual promiscuity and prudishness is a pretty common thing in human history.
*Ideally you can accuse them of both simultaneously. 
“I don’t always have illicit sex, but when I do, it’s with many goats, both male and female. Stay gentile, my friends.”
A problem with most of the posted ideas is that this prohibition does not apply to ANY combination of fabrics. It ONLY applies to wool and linen, as explained in the quote from Deuteronomy. Some might think that wool and linen are merely an example of a forbidden mixture, but that would be a mistake; they are the only forbidden mixture of fabrics.
Wool with silk and cotton - no problem. Linen with silk and cotton - again, no problem. Just don’t mix the silk and cotton.
If anyone wants to learn more about this, one place to start would be the English-language Wikipedia article on Shatnez.