Midrash for Bava Metzia 61:11
ותיפוק ליה משום אבידת גופה דדלמא קטלו לה באתרא דמתרו והדר קטלי ודלמא אתרו בה אי אתרו בה ולא אזדהרו בה ודאי אבידה מדעת היא:
IF ONE FINDS AN ASS OR A COW, etc. This is self-contradictory. You say. IF ONE FINDS AN ASS OR A COW FEEDING BY THE WAY, IT IS NOT CONSIDERED LOST PROPERTY: hence, only when feeding by the way are they not [regarded as] lost; but if running on a road, or feeding among the vineyards, they are considered lost! Then consider the second clause: [BUT IF HE FINDS] AN ASS WITH ITS TRAPPINGS OVERTURNED, OR A COW RUNNING AMONG THE VINEYARDS, THEY ARE CONSIDERED LOST; hence, only if running among the vineyards are they lost; but if running on the road, or feeding among the vineyards. they are not lost! — Said Abaye: His companion telleth it concerning him:<span class="x" onmousemove="('comment',' Job XXXVI, 33; (E.V.: the noise thereof sheweth concerning it), i.e., each clause illumines the other. ');"><sup>10</sup></span>