Leviticus 23:21-22

And ye shall make proclamation on the selfsame day; there shall be a holy convocation unto you; ye shall do no servile work: it is a statute for ever in all your dwellings throughout your generations. And when ye reap the harvest of your land, thou shalt not wholly reap the corners of thy field, neither shalt thou gather the gleaning of thy harvest: thou shalt leave them for the poor, and for the sojourner: I am Jehovah your God.