The tithe (Hebrew: מעשר; ma'aser) is specifically mentioned in the Books of Leviticus, Numbers and Deuteronomy. The tithe system was organized in a seven-year cycle, the seventh-year corresponding to the Shemittah-cycle in which year tithes were broken-off, and in every third and sixth-year of this cycle the second tithe replaced with the poor man's tithe. These tithes were akin to taxes for the people of Israel and were mandatory, not optional giving. This tithe was distributed locally "within thy gates" to support the Levites and assist the poor. Every year, Bikkurim, terumah, ma'aser rishon and terumat ma'aser were separated from the grain, wine and oil. Initially, the commandment to separate tithes from one's produce only applied when the entire nation of Israel had settled in the Land of Israel. The returnees from the Babylonian exile who had resettled the country were a Jewish minority, and who, although they were not obligated to tithe their produce, put themselves under a voluntary bind to do so, and which practice became obligatory upon all.

The first record of tithing in the Torah appears in Genesis 14:20, where Abraham gave "a tenth of everything" to Melchizedek.

The obligation of separating the respected portions and giving them to the designated parties (priests, Levites and Israelites) applies to six years out of the seven-year cycle. With respect to the Second Tithe, it was permitted to redeem their value in money for a later time when the owner is able to buy therewith fruits in Jerusalem and to eat them there, within the walls of the city. Fruits and vegetables are exempt from tithing during the Seventh Year, but during the other six years, the obligation to tithe begins with the ripening of most fruits and when they are brought within the owner's house.

Under certain conditions, some harvested fruit and grain can still be eaten temporarily, without tithing. For example, if grapes were intended to be eaten fresh, their ripening determines when they must be tithed. If, however, the owner intends to make wine from the grapes, the fresh grapes can still be eaten without tithing, until such time that the owner has pressed the grapes and he removes the stems, peels and seeds from the wine cask, in which case it signals its final preparation (גמר מלאכה‎), when the wine must be tithed. Figs require tithing when they become ripe, but if the owner intends to make fig-cakes from them, they can be eaten fresh without tithing until such time that he either smooths out the surface of the fig-cake that lays within its round mold, in which case the obligation to tithe them begins. Most fruits from trees (excluding olives) can be tithed the moment the fruit begins to ripen on the tree (Hebrew: חנטה). Grain and olives become liable to tithes when they have reached at least 1⁄3 of their potential growth. After harvesting, wheat is tithed once the grain has been separated from the husks and has been gathered together into a heap by the winnowing fork, or put within a granary. Until then, the grain may be temporarily eaten without tithing. If one tithed grain, he must still separate the Challah dough-portion, when baking a quantity of bread. Vegetables require tithing by a rabbinic decree when they are picked.

If oil were to be pressed from the harvested olives, one may still temporarily make use of the oil that collects in the lower millstone and within the frails without tithing. Oil, however, that falls into the vat requires tithing before it can be consumed.

This offering is sometimes called the priestly dues, as it is intended for the priests of Aaron's lineage. The first obligation that was incumbent upon an Israelite or Jew was to separate from his harvested grain, such as wheat, barley, or spelt, wine (including unpressed grapes) and oil (including unpressed olives) the one-fiftieth portion of these products (or one-fortieth, if he were a man of generosity; and one-sixtieth if he were stingy) and to give the same to a Kohen, a priest of Aaron's lineage, who, in turn, would eat such fruits in a state of ritual cleanness, in accordance with a biblical command, "...and let him not eat of the holy things, until he bathes his flesh in water. And when the sun goes down, he will be clean, and shall afterward eat of the holy things because it is his food".

The tractate Terumot of the Mishnah and of the Jerusalem Talmud formulates the Jewish religious law for this gift, specifying two kinds of terumot given to the priest: the regular offering, known also as the terumah gedolah ("great heave-offering"), which the Israelites were required to give to the priest from the produce of their fields, and the terumat ma'aser ("tithe of the heave-offering"), the gift that the Levites were required to put aside for the priests from the tithe which ordinary Israelites had been required to give to them.

This obligation was contingent upon the fact that such fruits grew in the Land of Israel. Later, the Rabbis made it an obligation to do the same for all fruits and vegetables grown in the Land of Israel, and not only to such fruits as grain, grapes and olives.