Do not cook a kid in its mother’s milk (Exodus 34:26)
Yes, this mitzvah looks a lot like Mitzvah #92, but there are actually three discrete prohibitions regarding milk-and-meat combinations: (1) not to cook them together; (2) not to eat such a mixture; (3) not to benefit from such a mixture. (We may have benefit from some types of forbidden foods but not from others.) Mitzvah #92 is the prohibition against cooking such a thing, while this mitzvah is the prohibition against eating or otherwise deriving benefit from it.
The prohibition of benefit is evident from the fact that the Torah doesn’t just prohibit eating such a combination, it objects to bringing it into existence at all. So, while we may feed non-kosher meat to our animals or sell it to non-Jews neighbors so long as we do not eat it ourselves, we may not derive such forms of benefit from milk and meat. So don’t cook veal parmesan, don’t eat spaghetti with meatballs all covered with cheese, and if such things come into your possession, just throw them away.
The Talmud in Chulin (115b) ascribes each prohibition of meat-and-milk (cooking, eating and benefit) to a separate instance of “Do not cook a kid…” in the Torah: the two we’ve had so far, plus the one found in Deuteronomy 14:21. Nevertheless, it only counts as two mitzvos, with our verse here serving “double duty” for both eating and benefit. This is because, as the Talmud teaches in Pesachim (21b), things that are prohibited to eat are also prohibited as sources of other types of benefit unless specifically permitted. So, for example, we may give or sell non-kosher meat to non-Jews or feed it to our animals only because such benefit was expressly permitted by the Torah (in Deut. 14:21 and Exodus 22:31, respectively).
Of course, if a prohibition on eating normally includes other forms of benefit, one might question why the Torah needs to state this mitzvah three times rather than twice. The reason is because of the phraseology used by the Torah. The Talmud tells us that “you shall not eat” includes benefit, but the prohibition on meat-and-milk is phrased “you shall not cook.” The third instance clarifies that the rule of “you shall not eat” prohibitions regarding other forms of benefit applies here as well. [The next question then is why the Torah doesn’t say “you shall not eat” for this mitzvah. There are other legal ramifications to the choice of words; see the Rambam’s Sefer HaMitzvos and the Sefer HaChinuch for a full elaboration.]
The underlying rationale for this mitzvah was discussed in Mitzvah #92: God has warned us away from things that are spiritually harmful the same way a doctor warns us about things that are physically harmful. This is a very important mitzvah and the Sages set a number of “fences” around it to keep us far from violating it. One example of this is the obligation to wait a certain period of time between eating meat and dairy (see Talmud Chulin 105a).
This mitzvah applies to both men and women in all times and places. It is discussed in the Talmudic tractates of Chulin (115a-b), Nazir (37a) and Pesachim (24b) and is codified in the Shulchan Aruch in Yoreh Deah 87. It is #187 of the 365 negative mitzvos in the Rambam’s Sefer HaMitzvos and #92 of the 194 negative mitzvos that can be fulfilled today as listed in the Chofetz Chaim’s Sefer HaMitzvos HaKatzar.