Musar su II Cronache 31:4

The pillar of תורה is dealt with in the legislation denying the tribe of Levi a share in the land to be distributed amongst the other tribes. It is their task to study Torah and to teach it, as we know from Deut. 33,10:יורו משפטיך ליעקב ותורתך לישראל, “They shall teach Your laws to Jacob and Your instructions to Israel.” If the Torah had allocated them farmland and orchards they would be so busy tending their land that they would not be able to fulfil their spiritual tasks. This is why the Torah instructs the Israelite to give certain gifts to the Levites so that they should be free of the burden of earning a livelihood and shoulder the burden of Torah study, etc., instead. Once the priests had increased in number their service in the Temple was restricted to a few days a year for each shift. On the festivals however, when they were in Jerusalem anyways, they could then receive a share of the meat of the many offerings presented on the altar. They made their regular living from the portions of meat set aside for them from animals slaughtered for private consumption as well as from the firstborn male animals, the first shearings, the Terumah (approx. 2% of the farmer's grain, oil and grape harvest). The Levite also contributed to the priest 10% of the tithes received.