ציטירנדיקער פּירוש אויף בראשית 38:20

פרט לחיה ולעוף ולבהמה טמאה – a “kid,” excluding fowl which is not cattle. A “kid,” excluding a beast of chase, and even though a beast of chase is included within cattle. An additional Biblical verse comes to exclude it. A “kid,” and not unclean cattle, and we derive if from what is written (Genesis 27:16): “with the skins of the kids;” “Judah sent the kid [by his friend the Adullamite]” (Genesis 38:20) – here the Biblical verse explains to you that this “kid” is from the goats. But if he did not explain this, there is by implication, even the rest of the cattle, hence it was necessary for him to explain this.

the first: ... And [Rashi] said that gedi (kid) is a young tender animal, and that this noun is [also] said for a young ox or sheep. And his proof is (in Genesis 38:20, where it states), gedi of the goats - for what [else] is the need for its qualification? But it is not like this, as only something from the species of goats is called a gedi. And in Arabic, it is [also] gedi, and it is not said for another species [besides goats]. However there is a difference between gedi and gedi of the goats; as the gedi is bigger than the gedi of the goats, such that [the latter] still needs to be with the [adult] goats. Hence, gedi and gedi of the goats. And the Sages received a tradition that Jews not eat meat with milk (as well as not to cook meat with milk). And now I will explain: You should know that the custom of the Torah is to speak about what is common. [For example with,] "the daughter of an ostrich" (Leviticus 11:16), why did Scripture alter it to say it like this? And does the daughter encompass the whole species? And we have not found it like this [with other species]. You should know that ostrich meat is dry like wood; and [so] it is not customary for people to eat it, as it has no moisture in it. And the only thing that is eaten from all of the species is the daughter - since it is female and young, it has a bit of moisture. But the young male does not. Likewise, people do not eat meat with milk, as it is not a pleasant food. As meat only gets cooked after a long time, and milk is not [quick to cook]; such that it is not the custom in the lands of Yishmael to this day for people to eat veal cooked in milk. [This is] because there is much moisture in veal, like there is [also] in milk, and so it is injurious - hence it is not eaten. But because gedi meat does not have moisture and it is warm when it is young, they therefore cook it in milk. And do not wonder, on account of it not being the custom of the people in these places to eat the gedi of the goats. For the physicians concur that there is no meat [as good] as it, and they even permit sick people to eat it. And in Spain, the Land of Israel, Persia and Babylonia, they do eat it. This was also the custom of the ancient ones (to eat it): "Two good gedii of the goats" (Genesis 27:9); "and we shall make a gedi of the goats before you" (Judges 13:15); and the priests eat a gedi of the goats as a sin-offering. And since no one eats raw meat, it is forbidden to cook a gedi in its mother's milk.... And we do not have a need to seek the reason for its prohibition, as it is hidden from the eyes of the ones with understanding. Perhaps it was because it is cruel-hearted to cook a kid in its mother's milk, in the way of "Do not slaughter a sheep or an ox - it and its child on one day (Leviticus 22:28), and "do not take the mother upon the young" (Deuteronomy 22:6). And most people are not accustomed to having sheep, so they buy milk from the marketplace and the milk is from a collection of different sheep. [Hence] maybe the buyer of the gedi will not know where is its mother; and when he buys milk, maybe there is milk there that is from the mother of the gedi that he bought, so he would transgress. And [we are] stringent about any doubt [concerning a law] from the Torah. And behold even the Yishmaelites concur that if a gedi is cooked in its mother's milk, such that the lineage is the same, then [the meat] is more pleasant. And the verse is speaking about what is common. And behold the ancient ones, may their memory be blessed, were stringent to remove any doubt and they forbade [all] meat and milk. And the Lord that gave them wisdom should give them their full wage....

לא תבשל גדי THOU SHALT NOT COOK A KID — A calf and a lamb also are comprehended under the term גדי, for גדי means nothing more than a young tender animal, as you may gather from the fact that you will find in several passages in the Torah that the term גדי is used and that the writer felt it necessary specially to explain it by adding after it the word עזים, as, e. g., (Genesis 38:17) “I will send forth a גדי of the goats”; (Genesis 38: 20) “the גדי of the goats”; (Genesis 27:9) “two kids of the goats (גדיי עזים)”. This fact serves to show you that wherever גדי is mentioned without further description the term implies also a calf and a lamb. — In three different passages the law לא תבשל גדי is written: once for the purpose of prohibiting the eating of meat-food with milk-food, once to prohibit us from deriving any other benefit (besides eating) from such mixture, and once to prohibit the boiling of meat with milk (Mekhilta; Chullin 115b).