2,315. Which Prohibitions Do and Don't Combine
Maachalos Assuros 4:17
Counter to the previous halacha, different types of neveila do combine, a neveila combines with a treifa, and all non-kosher species of domesticated and wild animals combine. The meat of a neveila and of a non-kosher species, however, don’t combine. Accordingly, if someone takes from a neveila ox, a neveila deer and a neveila chicken, and he combines it into an olive-sized portion, he is liable to lashes if he eats it. Similarly, if he put half an olive-sized portion of neveila from a kosher species with half an olive-sized portion from a treifa, or half an olive-sized portion of a neveila with half from a live kosher animal (which is the functional equivalent of a neveila), he would be liable for eating it. Likewise, if he makes an olive-sized portion out of camel, pig and hare meat, he would be liable for eating it. Conversely, if one puts half an olive-sized portion of a neveila ox with half an olive-sized portion of camel, they don’t combine; the same is true in all comparable cases. Similarly, meat from non-kosher species of animals, birds and fish don’t combine because they’re all different prohibitions, proscribed by different mitzvos as was explained in chapter 2. However, all prohibited species of bird do combine with one another, as do all the prohibited species of domesticated and wild animals. The general rule is that when things are prohibited by the same mitzvah, they combine; by two different mitzvos, they don’t combine. The exception is a neveila and a treifa because being a treifa is the start of becoming a neveila.
Maachalos Assuros 4:18
Let’s say that a person eats the skin, bones, sinews, horns or hooves of a neveila, a treifa or a non-kosher species of domesticated or wild animal, or he eats the nails of a non-kosher bird from a place that wouldn’t bleed when they’re cut off, or he eats their placenta. While this is prohibited, he isn’t liable because they’re unsuitable to eat. They don’t combine with meat to form an olive-sized portion.