Reference for Bava Batra 107:5
ואמר שמואל האי מאן דפתח מיא בארעא אדעתא דארעא קני אדעתא דכוורי לא קני היכי דמי פתח תרי בבי חד מעייל וחד מפיק אדעתא דכוורי חד בבא אדעתא דארעא
if his purpose is [to prepare] the soil [for ploughing] he thereby acquires ownership, but if he only wants to make threshing floors, he does not acquire ownership. How can we tell [which is which]? — If he has taken earth from the protuberances and thrown it into the depressions, then we know that his purpose is [to prepare] the soil,<span class="x" onmousemove="('comment',' Because he levels the whole field. ');"><sup>5</sup></span> but if he merely smoothes out the protuberances or levels up the hollows, we know that he intended to make threshing floors.<span class="x" onmousemove="('comment',' Because he still leaves different parts of the field at different levels. ');"><sup>6</sup></span>