Reference for Deuteronomy 24:19

Rabbi Yishmael declared three things before the Sages in the vineyard at Yavneh: Concerning an egg which was beaten together, and placed on vegetables of terumah that it acts as a connection; but if it was in the form of a helmet it does not act as a connection. And concerning an ear of corn in the harvesting, the top of which reached the standing corn that if it can be reaped together with the standing corn, it belongs to the owner; and if not, it belongs to the poor. And concerning a small garden which was surrounded by a row of vines that if it has space for the grape-gatherer and his basket on one side, and space for the grape-gatherer and his basket on the other side, it may be sown with seed; but if not, it may not be sown with seed.