Makkot 14B

מ״אחותו״ דרישא.

from the term “his sister” at the beginning of the verse (Leviticus 20:17), as the verse could have been formulated: And a man who takes the daughter of his father or the daughter of his mother, and there is no need to mention a sister at all. Liability for sex with a woman who is the daughter of both his father and his mother is derived from the term “his sister.”

ואידך: ההוא מיבעי ליה, לחלק כרת למפטם ולסך.

And according to the other opinion of the Rabbis, since nothing relevant to the topic of sex with one’s sister is derived from the term “sister,” that term is necessary in order to derive an unrelated matter, i.e., to divide the various prohibitions and establish liability for either one who blends anointing oil or for one who applies anointing oil to receive karet, if he performed either intentionally, and to bring a sin-offering if he performed either unwittingly, even though only a single punishment of karet is written in the verse: “A man who blends a mixture like it and who places any of it upon a non-priest, and he should be excised from his people” (Exodus 30:33).

ואידך? סבר כרבי אלעזר אמר רבי הושעיא, דאמר רבי אלעזר אמר רבי הושעיא: כל מקום שאתה מוצא שני לאוין וכרת אחד ⁠– חלוקין הן לקרבן.

And the other, R' Yitzḥak, holds in this regard in accordance with that which R' Elazar says that R' Hoshaya says, as R' Elazar says that R' Hoshaya says that there is a principle: Any place where you find two different prohibitions and one punishment of karet stated concerning them, they are distinct with regard to liability to bring an offering; if he performed both unwittingly, he is liable to bring two sin-offerings. According to R' Yitzḥak, there is no need for an additional derivation to render one who unwittingly blends and applies anointing oil liable to bring two sin-offerings.