Reference for Bava Metzia 203:8

הכא במאי עסקינן בחצר שאינה משתמרת

An objection is raised: If a man declared, 'Any lost property that may enter therein to-day, let my courtyard effect possession thereof on my behalf,' his declaration is valueless. Now if R. Jose son of R. Hanina's ruling, that a man's courtyard effects a title on his behalf even without his knowledge, is correct, why is his declaration valueless? — The reference here is to an unguarded courtyard.<span class="x" onmousemove="('comment',' Which cannot effect possession; v. supra loc. cit. ');">⁸</span>

Jastrow

Jastrow

Rashi on Deuteronomy