Reference for Bava Batra 284:8

ההוא דאמר לדביתהו נכסי לבני דיהוו לי מיניך אתא בריה קשישא אמר ליה ההוא גברא מאי תיהוי עליה אמר ליה זיל קני כחד מברא הנך ודאי לא קנו דאכתי ליתנהו

Samuel said to R. Hana of Bagdad: 'Go. bring me a group of ten [people] and I will tell you in their presence<span class="x" onmousemove="('comment',' To give the matter due publicity. ');">²⁰</span> [that] if possession Is given to an embryo [through the agency of a third party]. it does acquire ownership'. But the law is that if possession is given to an embryo [through the agency of a third party]. it does not acquire ownership. Once a certain man said to his wife, 'My estate [shall belong] to the children that I shall have from you'. His eldest son<span class="x" onmousemove="('comment',' From his first wife. ');">²¹</span>

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