Talmud for Yevamot 41:19
ורב מאי טעמא לא חשיב ליה מיחלפא ליה באשת אבי אביו
is permanent;<span class="x" onmousemove="('comment',' Lit., 'it is definite to him'. ');"><sup>47</sup></span> that of the other is not.<span class="x" onmousemove="('comment',' The daughter of his mother-in-law is permitted to him after the death of her sister, his wife. ');"><sup>48</sup></span> Rab said: Four [categories of] women [forbidden in the second degree] are subject to a limitation.<span class="x" onmousemove="('comment',' Lit., 'break' i.e., only they themselves are forbidden but not their descendants or ancestors in the descending or ascending line. In the case of the other relatives in the second degree of incest the prohibition extends throughout all generations in the ascending. and descending lines. ');"><sup>49</sup></span>