Reference for Bava Batra 337:8
אם כן נפישי עליה בעלי דינין
— [The precaution was] necessary [in the case] only<span class="x" onmousemove="('comment',' Lit., 'not necessary (but)'. ');"><sup>25</sup></span> where one asserts a claim by virtue of his paternal rights.<span class="x" onmousemove="('comment',' Lit., 'when he comes from the power of his fathers', i.e., the reason why a duplicate of a deed of purchase and sale is not issued, is not, as has been assumed, because a creditor might conspire to obtain double payment; but to provide against an heir who might prove by witnesses that a buyer had purchased a field from a seller who had robbed it from his father and in consequence of this proof it would be returned to him, while the buyer would be given a certificate authorising him to seize the property which anyone may have purchased from the same seller after the date of his purchase. Such a buyer, were he allowed a duplicate of his deed of purchase, could form a conspiracy with the heir by asking him to wait for a certain period, until he had been firmly established in the ownership of the field which he seized by virtue of one of the two copies of the deed and, after the whole affair had been forgotten, to claim again that field so that the buyer could, with the aid of the second of his two copies of the deed, seize the lands of other subsequent buyers. Hence R. Safra's ruling that no two deeds may be written in respect of one field. ');"><sup>26</sup></span> R. Aha of Difti said to Rabina: Why [should it be necessary]<span class="x" onmousemove="('comment',' In giving a reason why R. Safra forbids the issue of two deeds of purchase in respect of the same field. ');"><sup>27</sup></span> for him<span class="x" onmousemove="('comment',' The buyer who, as has been stated above, might form a conspiracy with a creditor to defraud subsequent buyers by means of the duplicate of his deed of purchase. ');"><sup>28</sup></span>