Leviticus 23:21-22

21And ye shall proclaim on the same day, that it may be an holy convocation to you: ye shall do no servile work in it: it shall be a statute for ever in all your dwellings throughout your generations. 22And when ye reap the harvest of your land, thou shalt not make clean riddance of the corners of thy field when thou reapest, neither shalt thou gather any gleaning of thy harvest: thou shalt leave them to the poor, and to the stranger: I am the LORD your God.