Reference for Sanhedrin 150:18

למ"ד שריפה חמורה איכא למיפרך

— Abaye answered: The Writ sayeth, [The nakedness of thy father, or the nakedness of thy mother, shalt thou not uncover'] she is thy mother — 18 teaching: thou canst punish for [incest with] his mother, but not with his mother's mother. Raba said: Whether we maintain, 'judge from it in its entirety', or<span class="x" onmousemove="('comment',' Lit., 'whether according to the one (Tanna) who says&nbsp;… or whether according to the one who says etc.' ');">¹⁹</span> 'judge from it, and place it on its own basis', this could not be deduced.<span class="x" onmousemove="('comment',' A verse is unnecessary, because his maternal grandmother could not be deduced from the gezerah shawah based on zimmah, whatever view be held on the scope of a gezerah shawah. There are two views on this. One is that the identity of law taught by a gezerah shawah must hold good in all respects, so that the case deduced is equal to the premise in all points; this is called 'judge from it and from (all) of it'. An opposing view is that the analogy holds good only in respect of the main question at issue, but that thereafter, the case deduced may diverge from its premise. This is called, 'judge from it, but place it on its own basis', i.e., confine the analogy to the main question, not to the subsidiary points. ');">²⁰</span> For on the view, 'judge from it in its entirety', [the deduction would proceed thus:] Just as her [his wife's] maternal grandmother is forbidden [to him], so is his maternal grandmother forbidden. [Then carrying the analogy] to its uttermost, just as in her case [i.e., incest with the former] is punished by fire so in his case [i.e., incest with the latter] is punished by fire. But on the view<span class="x" onmousemove="('comment',' Lit., 'but according to the one Tanna who says that, etc.' ');">²¹</span> that burning is severer [than stoning]. This analogy can be refuted. [Thus:] Why is her case [forbidden]?<span class="x" onmousemove="('comment',' I.e., the reason that his wife's maternal grandmother is forbidden on pain of burning. ');">²²</span> Because her [his wife's] mother is similarly forbidden.<span class="x" onmousemove="('comment',' Hence, since the prohibition of his wife's mother is so severe, it is natural that it should extend to her maternal grandmother too. ');">²³</span> But can you say the same in his case, seeing that his mother is forbidden [only] on pain of stoning!<span class="x" onmousemove="('comment',' Surely not! Since the prohibition is weaker, its punishment being more lenient, its extent too may be more limited, and not include his maternal grandmother. ');">²⁴</span> Moreover, his mother is forbidden on pain of stoning: shall his mother's mother be forbidden on pain of burning!<span class="x" onmousemove="('comment',' Surely there cannot be a severer punishment for the latter, a more distant relative, than for the former. Yet if the latter be derived at all by this gezerah shawah, the punishment must be burning, on this view that the analogy must be carried through on all points. ');">²⁵</span> Further, just as in her [his wife's] case, you have drawn no distinction between her mother and her mother's mother [both being forbidden on pain of burning], so in his, no distinction must be drawn between his mother and his mother's mother.<span class="x" onmousemove="('comment',' Just as incest with his mother is punished by stoning, so with his mother's mother. But making the analogy from another angle, the latter should be punished by burning, as has already been shewn. Hence, by a reductio ad absurdum, we are forced to dismiss the entire analogy. ');">²⁶</span> And on the view that stoning is severer, the analogy cannot be deduced because of this last difficulty.<span class="x" onmousemove="('comment',' Though the former two do not arise. ');">²⁷</span> Whilst on the view, 'judge from it and place it on its own basis,' [the deduction would proceed thus:] Just as her [his wife's] maternal grandmother is forbidden [to him], so is his maternal grandmother forbidden. But 'place it on its own basis', thus: in the former case the punishment is burning; but in the latter, stoning, the penalty which we find prescribed for incest with his mother. Now, on the view that burning is severer, this can be refuted,

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