Reference for Bava Batra 328:4
קא סבר אין כותבין שובר
[the creditor] might reply to him, 'I lost it', and would write out for him [instead], a receipt; and when the time of its payment<span class="x" onmousemove="('comment',' Lit., 'its time'. ');"><sup>9</sup></span> arrived, he<span class="x" onmousemove="('comment',' The creditor. ');"><sup>10</sup></span> might convert it [into] a plain [deed] and say to him, 'You borrowed from me now'!<span class="x" onmousemove="('comment',' I.e., after the date of the receipt. By converting the folded, into a plain deed, its date is moved a full year forward, and the receipt is thus made to appear as having been given prior to the loan. The creditor is, consequently, in a position to assert that the receipt was given for a previous loan, and to claim payment for the loan recorded on the deed. How, then, in view of such possible fraud, could R. Hanina allow the conversion of a folded, into a plain deed? ');"><sup>11</sup></span> — He holds the view that a receipt is not written.<span class="x" onmousemove="('comment',' If the creditor cannot produce and return the deed he is not entitled to the re-payment of his debt. ');"><sup>12</sup></span>