An observant Jew may not eat a cheeseburger. Every Jew knows that. What they may not realize is that the basis for the inflexible separation of meat and milk is not based on clear instruction, either from above or from anywhere else.
The complexities of Jewish dietary laws, including separating milk and meat, did not spring up ex nihilo. The customs evolved gradually, from the primeval beginnings of Judaism thousands of years ago until taking on their more or less current shape in Early Modern Europe. And it all began with one obscure verse in the Hebrew Bible, a verse about a baby goat, which appears however no less than three times: “Thou shalt not seethe a kid in his mother's milk” (Exodus 23:19; 34:26; Deuteronomy 14:21). But what does that mean?
The fact is, this verse is not clear, and its meaning has been debated for millennia by sages and greats, including Philo, Rabbi Akiva, Maimonides, St. Augustine, Martin Luther, Julius Wellhausen, and Jacob Milgrom, to name just a few. The result has been quite a few theories.
Recipes from the pagan kitchen
The traditional view is that this verse was God’s way of saying Jews should keep meat and dairy separate. Why God would decide to separate meat from dairy is not explained: He works in mysterious ways and who are we to question God.
Another theory, espoused by Maimonides and modern scholars, has it that boiling a kid in his mother’s milk was an ancient pagan practice that the ancient rabbis wanted to ban Jews from emulating.
A third theory espoused by Philo and many others since has it that boiling a suckling animal in the liquid that was meant to give it sustenance was cruel, hence the ban.
Yet another theory has it that the phrase “in his mother’s milk” originally meant “still suckling” and the meaning was: wait until the kid is weaned and only then may you cook and eat it.
None of these theories is satisfactory. If God wanted to tell Jews to keep meat and dairy separate, why didn’t he just come right out and say it?
Nor is there any evidence for a pagan rite of this kind; and if the writers of the bible wanted to compassionately ban cruelty to animals, why did it command that young animals be killed as sacrifices?
Similarly, if the Bible wanted to ban Jews from eating unweaned kids, why does it elsewhere say that a kid may be sacrificed from the age of eight days on, when it is certainly still suckling (Leviticus 22:27)?
Yet another possibility, first recorded in the 9th century biblical commentary by the Karaite scholar Benjamin Nahawandi, is that none of these theories are right, and the sentence has been misunderstood.
Hebrew is written without vowels, which makes the text susceptible to misreading.
Readers of English take vowels for granted. But if you take the word "bell" and take away the "e", for instance, you are left with BLL, which could be read as ball, bell, bill, boll or bull! It could even be bulla, belle, Billy, and so forth. You cannot possibly know which it is without context.
The key word in the verse in question has four consonants: T, B, Sh and L, which can theoretically be read in different ways. So this word could be interpreted as cook, boil or seethe; or using different vowel sounds, it could mean "to ripen," i.e., mature.
Given its context in the bible, that interpretation could make sense.
The verse first appears in in Exodus 23, not among dietary laws as one might expect but among laws governing sacrifices at the Temple on holidays. In this context, the meaning “mature” could make sense: Do not wait for the newborn livestock to be weaned, bring it to the Temple right away.
If this was in fact the original intention of the verse, it was misconstrued at a very early date.
Both references in Exodus place the prohibition in conjunction with the Temple sacrifice. The editor who placed the verse in Deuteronomy, probably at the very beginning of the Second Temple period (the 5th or 4th century B.C.E.) put it into a section dealing with dietary laws. Clearly he read the verb in the verse to mean “boil”.
Whatever the original meaning of the verse, it seems that very early on, this verse was understood as a prohibition on literally cooking a young goat in his own mother’s milk. That is, it would have been fine if one cooked it in the milk of some other she-goat as long as it wasn’t his mother.
This seems to be the way the Jewish philosopher Philo of Alexandria understood the prohibition in the first century C.E., at the very end of the Second Temple period. He though makes the reach that "kid" means any baby mammal, including sheep and cows (Virtues 8:249–251).
We do not know when precisely the verse began to be interpreted as a prohibition on mixing meat and dairy. It may have been already interpreted this way by some Jews in the time of Philo, unbeknownst to him, or perhaps it only developed in the aftermath of the destruction of the Temple in 70 C.E.
What we do know is that in the second century C.E., when Targum Onkelos, the rabbinical sanctioned translation of the Torah into Aramaic, was made, that was the established reading. Onkelos translates the verse “You shall not eat meat in milk.” The goat and his mother were edited out for clarity.
The succinct interpretation provided in the Aramaic translation is elaborated upon in the Mishnah, a legal codex of Rabbinic Judaism redacted in about 200 C.E. According to the Mishnah (Hullin 8:1-2) the prohibition on eating meat in milk encompasses not only mammals but poultry too, but not fish and locusts.
The Mishnah in its accepted form is conflicted, however, about this inclusion of fowl, which of course do not lactate, also saying, “One who brings up fowl with cheese on the table does not transgress a negative commandment.” (Hullin 8:3) This more than implies that the verse on the kid and mother goat did not include fowl, for if it did, bringing fowl on the table with cheese would transgress that negative commandment.
Furthermore, the Babylonian Talmud (Hullin 116a) recounts a story about Rabbi Levi going to eat dinner at the house of Joseph the Fowler, who served him peacock head cooked in milk. When Levi tells this to his rabbi Abba Arika, he asks why Levi didn’t excommunicate Joseph then and there. Levi responds that he thought they practiced the law according to Rabbi Jose the Galilean, which excluded poultry since it doesn’t have mother’s milk. This story seems to show that the view that chicken may be eaten with dairy was suppressed some time in the 3rd century or so.
Wait for it
Once it was established that meat, including poultry, may not be eaten together with milk or any milk products, the next issue that the rabbis tackled was the technical question of how to achieve the separation of eating cheese and meat. This seems to have been a matter of debate during Talmudic times (3rd to 5th centuries).
According to the Talmud (Hullin 104b), all that is required between eating meat and eating dairy is that one wash his hands and wash out his mouth. On the next page (Hullin 105a), Rabbi Assi asks Rabbi Johanan bar Nappaha how long one must wait between eating meat and cheese, and Johanan, the greatest rabbi of third century Palestine answers, “no time at all.” This was apparently the rule accepted by the rabbis in Palestine.
The rabbis in Babylonia on the other hand seemed to have come to a different conclusion.
The Babylonian rabbis thought that a period of waiting must be observed at least between eating meat and dairy. No wait is necessary between eating dairy and then meat, they concluded, based on a saying of Rabbi Hasda. The rabbis of Babylonia concluded that Johanan must have been talking about meat following cheese, but not cheese following meat, though this is in fact not actually stated.
However, the rabbis of Babylonia seem to have not decided what the exact time period one must wait between eating meat and eating dairy. A statement made by Mar Ukva in the same Talmudic section states that the more pious waited a day and less pious waited shorter periods of time.
Apparently, the more lenient view of the Palestinian rabbis made its way to northern Europe (modern-day northern France and Germany) in the Late Middle Ages (11th to the 13th centuries). The Jewish communities there did not observe a waiting period between meat meals and dairy meals - as long as they were separate meals. Even if they were back to back, it was fine.
On the other hand, the more stringent Babylonian tradition requiring a waiting period from meat to cheese took root in southern Europe (modern-day Spain and southern France). Eventually, this was codified by Maimonides in the 12th century as a six-hour wait, which is still the tradition among Sephardic Jews.
Another important development appeared in Europe in the 12th or 13th century. The rabbis of the period decided that certain cooking vessels absorbed the flavor of the meat or the dairy cooked in them for 24 hours. Thus they argued, using these vessels for cooking the other within the same 24 hours could constitute a violation of the meat in dairy rule and thus was forbidden. Gradually this rule concerning cooking vessels developed into the practice of keeping separate cookware, dishes and cutlery for meat and dairy over time, which is the practice today.
In later generations (15th and 16th centuries) the proliferation of the clock in Europe led to the adoption of a set period for waiting in northern Europe too, though only for an hour, not six as in the Sephardic tradition). But in later generations (17th to the 19th centuries), various Ashkenazi communities adopted longer waiting periods, typically three hours in the case of German communities, six hours in Eastern Europe, and famously in the case of Dutch Jews, only one hour.
Thus the small seed planted in antiquity - an obscure verse about a baby goat in the Bible - grew into a massive tree of regulations, rules and traditions dictating what Jews may and may not eat.