Mishnayos Bechoros Perek 1 Mishnah 2

פרה שילדה כמין חמור וחמור שילדה כמין סוס פטור (a cow that gave birth to a donkey of so) – if [the Mishnah] taught [only] “a cow that gave birth to a donkey of sorts” but did not teach “a donkey that gave birth to a horse of sorts,” I might say that the cow that gave birth to a donkey of sorts is that which is exempt from [their offspring being counted] as a firstborn, because they are not at all similar to each other, for this one (i.e., the cow) has horns and that one (i.e., the donkey) does not have horns, for this one (i.e., the cow), its hoofs are cloven but that one (i.e., the donkey), its hoofs are closed, but a donkey which gave birth to a horse of sorts, I might say that that it (i.e., the horse of sorts) is a red donkey and it is obligated [for its offspring to be counted as a firstborn]. But if it (i.e., the Mishnah) had only taught the concluding clause and did not teach the opening clause, I would say that the donkey that gave birth to a horse of sorts is exempt from [its offspring being counted as a firstborn] because a horse is not sanctified with a firstborn, but a cow that gave birth to a donkey of sorts where both of them are sanctified through the firstborn, I might say that it (i.e., the donkey of sorts) is obligated [for its offspring to be counted as a firstborn. Therefore, both phrases are necessary.

פטר חמור פטר חמור שני פעמים – one in “Sanctify to me all firstborns” (Exodus 13:12) and the other in (the beginning of the Torah reading for Shabbat Hol HaMoed Passover and Sukkot – beginning with Exodus 33:12 and extending to Exodus 34:26) “See you say to me,” (Exodus 34:20).

מהו באכילה – that is to say, an animal where the birth mother is not similar to the animal born- what is the Halakha with regard to their consumption/eating?

שהיוצא מן הטמא טמא – and the honey of bees and hornets. It is permitted and is not called that which comes out from the impure, because it does not squeeze/wring it out from their flesh but rather, they bring it into their bodies, since they consume from the flours of the trees and from them the honey is made. But the milk of a human is permitted as I explained, but to suck from the breasts of a woman is prohibited. And all the rest of the milk of impure animals and wildlife, they come from that which is impure and is forbidden.

דג טמא שבלע דג טהור – even though we did not see it that it swallowed it, for since most fish breed with their own kind, it is like it swallowed in our presence.