Related for Yevamot 178:5

א"ל ואת לא תסברא והתנן הולד ממזר מזה ומזה בשלמא משני ממזר אלא מראשון אמאי אשתו היא וישראל מעליא הוא וקא שרינן ליה בממזרת

that this is a preventive measure against the possibility 'that one might wilfully neglect to set apart [the <i>terumah</i> from the remainder]'; is there anywhere [I may ask] a law that <i>terumah</i> which is Pentateuchally valid should, owing to the possibility that one might wilfully neglect his duty, be turned into<span class="x" onmousemove="('comment',' Lit., 'they brought it out', ');">¹³</span> unconsecrated produce?<span class="x" onmousemove="('comment',' Hullin v. Glos. ');">¹⁴</span> Could, then, a <i>Beth din</i> lay down a condition that would cause a law of the Torah to be uprooted! — The other replied: And do you not yourself agree with such a ruling? Have we not learned, THE CHILD BY THE ONE HUSBAND OR THE OTHER IS A BASTARD. Now, it is reasonable [that the child] by the second [should be deemed] a bastard,<span class="x" onmousemove="('comment',' Since, owing to the fact that the first husband was still alive, the marriage was unlawful. ');">¹⁵</span>

Explore related for Yevamot 178:5. In-depth commentary and analysis from classical Jewish sources.