The Torah portion of Korach ends with an extensive discussion of the various tithes (agricultural taxes) that the Torah requires. The basic idea is that the Land of Israel and its agricultural products are considered holy, therefore there are special laws that apply to them. The most well known is the obligation in Biblical and Temple times to separate a percentage of the crop and give it to the Cohanim (Priests of the Holy Temple), the Levites and the poor. Some of the produce was separated from the crop and was supposed to be brought to Jerusalem, where it was eaten by the owners and by whomever they wanted to share it with. The distribution of the tithing worked according to a precise schedule that ran in seven-year cycles.
The most obvious lesson of the tithes is that the world and everything in it belongs to God and by obligating the farmer to either give away part of the crop or to eat it in a specific city, the idea that God, not the human being, is the ultimate landowner, was well learned. The other, more pragmatic purpose of the tithes was to support those who did not have land of their own, and who worked for the communal good. The Levites and the Cohanim were dedicated to working in the Temple in Jerusalem and to teaching Torah, and therefore they did not inherit land like the rest of the nation. Because of this, the Torah granted them the income from these taxes as their means of livelihood.
Another purpose of these agricultural laws is to inculcate in the Jewish people the positive character traits of compassion, justice and humility.
Today, since most Jews do not live in Israel and the Cohanim are not in a state of ritual purity (a prerequisite to eating tithed food), tithes are not given, nor are they eaten in Jerusalem. There is still an obligation, however, to separate the tithes from agricultural produce of the Land of Israel and dispose of them in a respectful fashion. The law requires that one separate a little more than 1% of any produce grown in Israel, and recite a declaration before the fruit or vegetables may be eaten. Even today, and even outside of Israel, one of the agricultural tithes is still fulfilled, albeit symbolically. When one makes dough, a small amount is taken off and burnt. In the times of the Temple, when the Cohanim were in a state of ritual purity, this separation, known as Challah, was given to them.
The Biblical laws of tithes only apply to agricultural produce. Jewish practice has extended the idea, however, to tithing one’s income as well. It has become the universal custom, (according to some authorities, it’s the law) that we give at least 10% of our income to charity. This practice is known as ma’aser kesafim, tithes of money. In setting aside a part of our incomes for charity in this way, we are acknowledging that our money was not earned through our efforts alone, but is a gift from God. As He has chosen to reward us with financial gain, it is our duty to share it with others.