Bekhorot 7A

אישתני מגמל שפיר דמי, או דלמא לא שנא?

it is different from an ordinary camel and has some characteristics of its mother, perhaps it is permitted to eat it. Or perhaps there is no difference, and with regard to consumption R' Shimon also requires that its head and the majority of its body resemble its mother.

תא שמע: בהמה טהורה שילדה מין בהמה טמאה ⁠— אסור באכילה, ואם דומה ראשו ורובו לאמו ⁠— חייב בבכורה. שמע מינה: לאכילה נמי בעי רבי שמעון ראשו ורובו!

The Talmud suggests: Come and hear a proof from a baraita: With regard to a kosher animal that gave birth to a non-kosher animal of sorts, the offspring is forbidden for consumption, in accordance with the opinion of R' Shimon; but if its head and the majority of its body are similar to its mother, it is obligated in, i.e., subject to the obligations of, firstborn status. Learn from it that with regard to consumption, R' Shimon also requires that its head and the majority of its body resemble the mother.

לא, לבכורה דוקא. דיקא נמי, דקא שבקה לאכילה וקם ליה אבכור. שמע מינה: לבכורה הוא דבעי רבי שמעון ראשו ורובו, אבל לאכילה ⁠— לא.

The Talmud rejects the proof: No, the requirement that its head and the majority of its body resemble the mother is relevant specifically with regard to firstborn status. The Talmud comments: The language of the baraita is also precise, as the tanna leaves the halakha of consumption with which he began and addresses the halakha of firstborn status. Learn from it that it is with regard to firstborn status that R' Shimon requires that its head and the majority of its body resemble the mother, but with regard to consumption he does not require this, and even a partial similarity suffices.

לעולם אימא לך: לאכילה נמי בעי, ובכורה איצטריך, סלקא דעתך אמינא: הואיל וכתיב ״אך בכור שור״, עד שיהא הוא שור ובכורו שור, ולא תיסגי ליה בראשו ורובו עד דאיכא כוליה, קמשמע לן.

The Talmud rejects this conclusion as well: Actually, I will say to you that with regard to the permissibility of consumption he also requires that its head and the majority of its body be similar to the mother. But it was necessary to state this condition specifically with regard to the halakha of firstborn status, as it might enter your mind to say that since it is written: “But the firstborn of an ox” (Numbers 18:17), perhaps firstborn status does not apply unless it is an ox and its firstborn is an ox, and a resemblance of the offspring’s head and the majority of its body to the mother does not suffice unless its whole body has the appearance of an ox. Therefore, the tanna teaches us that a resemblance of its head and the majority of its body to the mother do suffice.