Reference for Temurah 49:58

ואי סלקא דעתך שיירו משוייר הרי זה ולד שלמים

the action is not valid, and that an embryo is considered as the thigh of its mother; for this reason she obtains [freedom] in his behalf, since it is on a par with the case of one who freed a half of his slave,<span class="x" onmousemove="('comment',' Where the slave acquires possession of that half, and so here the bondwoman is privileged to secure the freedom of her child.');">⁴⁷</span>

Jastrow

Jastrow