Reference for Bava Batra 160:3
וחכמים אומרים אין כותבין עליה פרוזבול ואינה כקרקע ומקבלת טומאה במקומה והרודה ממנה בשבת פטור
and it is not subject to the laws of Levitical defilement, while in situ,<span class="x" onmousemove="('comment',' In accordance with the principle that whatever is attached to the ground [H] (in opposition to [H] detached') is not susceptible to the laws of levitical uncleanliness. ');"><sup>4</sup></span> and he who takes [honey] out of it on the Sabbath is under the obligation of [bringing] a sin-offering. But the Sages say: A <i>prosbul</i> may not be written on the basis of it, it is not regarded as landed property, it is subject to the laws of Levitical defilement in situ, and he who takes [honey] out of it on the Sabbath is absolved.<span class="x" onmousemove="('comment',' V. supra 656. ');"><sup>5</sup></span>