Reference for Bava Batra 336:7
אמר להו מאי אעביד לכו דאמר רב ספרא אין כותבין שני שטרות על שדה אחת דלמא טריף והדר טריף
He said to them: 'What can I do for you. when R. Safra said: Two deeds [may] not be written in respect of the same field [since a person] might [thereby] seize and seize again'.<span class="x" onmousemove="('comment',' Infra 169a. A buyer who purchased a field the sale of which has been secured by the seller's landed property might, if a creditor of the seller should ever seize that field for his debt, secure double compensation from the lands of subsequent buyers by the production in turn of one of the two deeds. ');"><sup>11</sup></span> [As] they were troubling him,<span class="x" onmousemove="('comment',' Persisting in their demand. ');"><sup>12</sup></span>