In Leviticus and Numbers, ma’aser (tithing) refers to a Temple tax; in Deuteronomy, however, it refers either to what must be brought and consumed on a pilgrimage festival or to charity. This dichotomy led the rabbis to design the cumbersome system of the first and second tithes (maaser rishon and maaser sheni).
The agricultural allocations for the poor outlined in Leviticus and Deuteronomy are a series of negative commandments, in which God forbids Israelite householders from gathering some of their produce and requires them to leave it for the poor. The rabbis took these laws a step further, granting the poor property rights over the allocations even before they are gathered.
Gregg E. Gardner