Chulin 7:5-6

Chulin 7:5

Let’s say that a gid hanasheh was cooked with permitted sinews and is recognizable. In such a case, the other sinews are prohibited if the gid hanasheh imparts flavor. If the gid hanasheh cannot be identified in the mixture, all the sinews are prohibited, as is the broth if the gid hanasheh was of sufficient size to impart flavor. The same applies to a piece of neveila and to a piece of non-kosher fish that were cooked with other pieces: if they are recognizable, they prohibit the other pieces if they impart flavor; if they are not recognizable, all the pieces are prohibited, as is the broth if the prohibited piece was of sufficient size to impart flavor.

Chulin 7:6

The law of gid hanasheh applies to kosher but not to non-kosher animals; Rabbi Yehuda says that it also applies to the non-kosher animals. Rabbi Yehuda said, “Wasn’t the gid hanasheh prohibited since the time of Yaakov’s sons, when non-kosher animals were still permitted to them?” The Sages responded that the law of gid hanasheh was actually given at Sinai, it was just written in the relevant place (i.e., following Yaakov’s wrestling with the angel).