Reference for Bava Batra 345:3

תנא דידן סבר אותיות נקנות במסירה ותנא ברא סבר אין אותיות נקנות במסירה

and the external<span class="x" onmousemove="('comment',' The Tanna of the Baraitha. ');">⁷</span> Tanna holds [that] 'letters' are not acquired by means of delivery.<span class="x" onmousemove="('comment',' The debtor can consequently refuse payment of the bond, pleading that he does not owe the money to the holder of the bond but to the other Joseph; while to the other he can refuse payment on the ground that he has no bond to prove his claim. ');">⁸</span> And if you prefer I would say that all<span class="x" onmousemove="('comment',' The authors of the Baraitha under discussion and of our Mishnah. ');">⁹</span>

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