Мидраш к Шмуэль Б 5:10

A righteous person will flourish like a date palm. No part of the date palm is wasted: Its dates are eaten; its young branches are used for ritual blessing [of the lulav on sukkot]; its fronds cover the Sukkah; its fibers are used to make ropes; its leaves are used for sieves; its planed trunks are used for roof beams. So too there are none worthless in Israel: Some are versed in the Bible; others know Mishnah; some are masters of aggadah [storytelling]; others do good deeds; still others promote social equity.