Reference for Chullin 261:42

שלשה שבתבואה

As to the corner (of the vineyard] this is inferred by the use of the expression 'after thee' both here [with regard to a vineyard] and also with regard to the olive-tree; for it is written: When thou beatest thine olive-tree thou shalt not go over the boughs after thee,<span class="x" onmousemove="('comment',' Deut. XXIV 20.');"><sup>33</sup></span>