Reference for Bava Metzia 144:13

היו לקוטות מארבע ולכל אדם משלש אין פוסקין עד שיצא השער ללוקט ולמוכר

at three, a contract must not be entered into [at a fixed maximum price] until the same market price has been established for the gleaner<span class="x" onmousemove="('comment',' I.e., the petty trader in gleanings. ');">²⁵</span> and the merchant.

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