Halakhah for Sanhedrin 149:6
<br><br><big><strong>הדרן עלך בן סורר ומורה</strong></big><br><br>
<b><i>GEMARA</i></b>. The Mishnah does not state, 'He who commits incest with a woman whose daughter he has married', but 'HE WHO COMMITS INCEST WITH A WOMAN AND HER DAUGHTER'; this proves that both are forbidden. Who are they then? His mother-in-law and her mother. Then the Mishnah further states, THERE IS INCLUDED IN 'A WOMAN AND HER DAUGHTER'; this proves that the first are explicit and the others derived.<span class="x" onmousemove="('comment',' The statement that a number of other women are included in the first cannot be literal, for in fact the meaning of 'a woman and her daughter' cannot be extended to include, e.g., his own daughter or his son's daughter. Hence it must mean that 'a woman and her daughter' are explicitly stated in the Bible, whilst the others are included as derivations from these two. Now since the wording of the Mishnah shows that both the first two are forbidden and that the only relation explicitly forbidden on pain of burning is his mother-in-law, it follows that 'a woman and her daughter' must mean his mother-in-law ('daughter') and her mother. And these are regarded as explicitly forbidden. ');"><sup>5</sup></span>