Reference for Chullin 275:7

וכמה נותן לו כו':

A Tanna taught: It does not mean that one must first bleach it and give it him, but that after the priest has bleached it there should be th weight of five sela's.<span class="x" onmousemove="('comment',' I.e., it is not incumbent upon an Israelite to give the priest bleached wool, but he must estimate such a quantity as would, after bleaching, make up five sela's weight.');"><sup>3</sup></span>