מכלל שנאמר וכל בהמה מפרסת פרסה ושוסעת שסע שתי פרסות מעלת גרה שומע אני שכל שאינה מעלת גרה ומפרסת פרסה אסורה. ולאו הבא מכלל עשה עשה הוא.
Normally, if someone transgresses a negative commandment he becomes liable for corporeal punishment if certain conditions are met. However, contravening a negative commandment that is derived from a positive commandment generally does not merit any corporeal punishment. However, the Torah also specifically prohibits animals that have only one characteristic (Siman), which again leads to the logical conclusion that those that have neither are of course prohibited. Since this prohibition is given in the negative form, eating all prohibited animals, whether those who lack both Simanim or only one Siman, makes one liable for corporeal punishment.
ובגמל ובחזיר ובארנבת ובשפן נאמר את זה לא תאכלו ממעלי הגרה וממפריסי הפרסה וגו' הרי למדת שהן בלא תעשה ואע"פ שיש בהן סימן אחד. וכל שכן שאר בהמה טמאה וחיה טמאה שאין בה סימן כלל שאיסור אכילתם בלא תעשה יתר על עשה הבא מכלל אותה תאכלו:
לפיכך כל האוכל מבשר בהמה וחיה טמאה כזית לוקה מן התורה.
The problem is that there is a general rule in Halacha that אין מזהירין מדין ק"ו, a prohibition that is derived through an extrapolation from a minor premise to a major one, (Kal Vechomer), which is the case here, does not warrant corporeal punishment. For a liability for corporeal punishment to take effect, the prohibition must be clearly stated in the negative. As the prohibition to eat animals lacking both Simanim is derived through a Kal Vechomer, there should be no corporeal punishment for transgressing. Why is this case different?
Rambam addresses this in his Sefer Hamitzvot Negative Commandment 172 by referring us to Negative Commandment 336 where he promises to explain it. He also comments that just like in that later case, the negative commandment is only a clarification.
אלא שקל וחמר זה לגלויי מלתא בעלמא הוא, כדרך שאמרו בבתו", כמו שנבאר במקומו
The Torah prohibits sexual relations with one’s granddaughter whether she is the daughter of a son or of a daughter. Nowhere does it expressly forbid relations with one’s own daughter whether she was born through marriage or out of wedlock. That prohibition itself is derived logically through a Kal Vechomer (according To Rambam – Rashi disagrees) while the corporeal punishment is derived through another hermeneutical process, a Gezeirah Shava. (I do not want to get into the particulars of this Derasha here and leave to the interested reader to look it up in sefer Hamitzvot ). Here the Halacha goes even a step further; the Kal Vechomer creates a separate negative commandment. After explaining the process, Rambam makes an interesting statement.
ולשון גמרא כריתות:
"אל תהי גזרה שווה קלה בעיניך, שהרי 'בתו' אחד מגופי תורה,
ולא למדה הכתוב אלא בגזרה שווה: אתיא הנה הנה אתיא זמה זמה".
והתבונן באמרם: לא למדה הכתוב, ולא אמרו לא למדנוה, לפי שכל הדברים האלה קבלה מפי השליח והוא פירוש מקובל, כמו שביארנו בהקדמת חיבורנו בפירוש המשנה, ולא שתק הכתוב מלהזכירה אלא מפני שאפשר ללמדה בגזרה שווה.
וזהו עניין אמרם:
"לא למדה הכתוב אלא בגזרה שווה".
ומספיק אמרם "גוף תורה".
Rambam notes that the Gemara refers to this prohibition as a גוף תורה – part of the body of Torah – in other words an integral commandment within Torah, which though not explicit it has the same status as an explicitly written commandment allowing for corporeal punishment. However, he notes that the hermeneutical derivation, the Gezeirah Shava, is not the basis for the separate commandment. That hermeneutical process, though it could have made the act a Torah prohibition (more on this later), would not have it counted as a separate commandment nor would it have allowed corporeal punishment. The basis for it being a separate commandment is that it is Pirush Mekubal, a revelation based explanation of the text that Moshe received directly from God. That gives this law the same authority as an explicitly written law. Rambam consequently offers an original interpretation of the Gemara statement "לא למדה הכתוב אלא בגזרה שווה. Traditionally it is explained that the Gemara is pointing out that a Gezeirah Shava is authoritative because it teaches a Guf Torah, a commandment. IOW it defines the authority of a Gezeirah Shava. Rambam notes that if that were the meaning the Gemara should have read -לא למדנוה - we, the Rabbis, do not know it except by using a GS. The Gemara reads - לא למדה – the Torah did not teach it. The Gemara is telling us that the Torah did not find it necessary to specifically teach this prohibition because it was taught orally and it relied on the GS as a mnemonic and/or as support, which is generally referred to as Assmachta. Rambam legislates it in Hil. Issurei Biah 2:6
The last words, ואינו מדברי סופרים – they are not of rabbinical origin – means that the derivation is not hermeneutical. It could be a Torah law and still be considered Divrei Soferim. IOW the Rabbis may derive a law logically through a Kal Vechomer and that law would have the authority of a Torah law, a De’oraita, but it would not be counted as a separate commandment nor would it make the transgressor liable for corporeal punishment. This law, because it is a revelation-based law, is not considered Divrei Soferim but Guf Torah and warrants to be counted separately. The hermeneutics, as Rambam explained in his introduction to Pirush Hamishna, is only for support.
שכולן פירושים מקובלים מפי משה. ועליהם ועל דומיהם אמרו, כל התורה נאמרו כללותיה ופרטותיה ודקדוקיה מסיני.
אבל אע"פ שהן מקובלים ואין מחלוקת בהם מחכמת התורה הנתונה לנו, נוכל להוציא ממנה אלו הפירושים בדרך מדרכי הסברות והאסמכתות והראיות והרמזים המצויים במקרא
אלא שקל וחמר זה לגלויי מלתא בעלמא הוא, כדרך שאמרו בבתו",
We now understand that לגלויי מלתא בעלמא הוא, means it is a Pirush Hamekubal that found support through hermeneutics. Both the prohibition to eat forbidden animals and the prohibition of sexual relationship with a daughter are in that category of Torah Sheba’al Peh and have the same authority as a written commandment.
We gained several insights working through this comment of Rambam. We have a clear case here of a category – Pirush Hamekubal – that Rambam defines in his introduction to Pirush Hamishna and is central to his understanding of what Torah Sheba’al Peh – the oral Torah is. It has the exact same authority as a written law including to be counted separately and also allows for corporeal punishment if transgressed.
We also learned that Divrei Soferim is not necessarily a rabbinic law, a Derabanan, but could have the authority of Torah law if it is derived logically or hermeneutically. It however cannot be counted as separate but rather as an extension of an existing law ( see Shoresh 2 in SHM) and has implications on the punishment a transgressor is liable.
The sugya of the prohibition of sexual relationship with a daughter is very complicated and I have just focused on one aspect of it according to Rambam. Rashi and other Rishonim understand it differently. I have followed Rambam here and his approach points to some very important basic concepts of what TSBP is.