Mishnayos Demai Perek 6 Mishnah 6

לא ימכור אדם זיתיו – olives hat became detached from the tree and were not susceptible to receive ritual impurity, as for example, they did not perspire/drip the dripping of the vat/pit where olives are packed until they form a viscid mass where it makes them susceptible to receive ritual impurity.

אלא לחבר – to separate that which is presumed/adhering to ritual purity and he will not sell them to someone who is not a member of the order for the observance of Levitical laws in daily intercourse/חבר and he will not tread/stamp upon them in ritual impurity.

אף למעשר – even to someone who did not accept upon himself other than to tithe but did not accept upon himself to be presumed/adhering to ritual purity can sell them, for since they yet are not susceptible it can stated that perhaps he ate them prior to their perspiring, for even though most of the olives are not ready to be consumed as such, by pretext, anything that we are able to hang on it, we hang upon it. But Maimonides establishes their dispute of that of the School of Shammai and the School of Hillel, for the School of Shammai holds that it is forbidden to cause ritual impurity to unconsecrated produce that is in the Land of Israel while the School of Hillel holds that it is permissible to cause ritual impurity to unconsecrated produce in the Land of Israel.

וצנועי בית הלל – the conscientiously pious ones who are exacting in observance of the commandments who were in the School of Hillel [and who followed the School of Shammai – who would not sell their olives to anyone other than someone who is a member of the order for the observance of Levitical laws in daily intercourse].