||The fundamental halakhot followed by all of Ashkenazic Jewry. Terumat ha-Deshen consist of 354 (a number corresponding to the numerical value of דשן and to the days of the lunar year) decisions in the form of responsa on synagogal, ritual, and legal subjects; and Pesakim u-Ketavim, containing 267 responsa, of which nearly one-third deal with the various rules regarding the marriage laws. Terumat ha-Deshen became the decisor in halakha and is extensively by all poskim from his generation forward.
R. Israel B. Isserlein b. Pethahiah (1390–1460), the foremost rabbi of Germany in the 15th century. R. Isserlein was also called, after the towns in which he resided, R. Israel Marburg and R. Israel Neustadt, but he was mainly known as "the author of Terumat ha-Deshen," his chief work. R. Isserlein, the great grandson of R. Israel of Krems (author of Haggahot Asheri), was born in Regensburg. His father died when Israel was a youth, so he was educated in Wiener-Neustadt in the home of his mother's brother R. Aaron Plumel (Blumlein). In 1421 his uncle and mother were killed during the Vienna persecutions. After staying for some time in Italy, R. Isserlein established his residence in Marburg, Styria. In 1445 he returned to Wiener-Neustadt where he was appointed rabbi and av bet din of the city and neighborhood. Here R. Isserlein spent the rest of his life, and through him Wiener-Neustadt became a center of study, attracting a large number of students, many of whom later served as rabbis in various communities. Outstanding scholars and communities addressed their problems to him and accepted his decisions. The most important posekim valued his books and highly praised his personality. R. Moses Mintz called him Nesi ha-Nesi'im ("chief of chiefs"; responsa, no. 12 Salonika, 1802 ed., 10b). R. Isserlein refused to accept a salary from his community. He opposed those rabbis who tried to dominate their congregants by threats of excommunication. Through his efforts and personal authority he prevented a controversy among the German communities of the Rhine district when R. Seligman of Bingen attempted to impose various takkanot on them enacted on his responsibility, and threatened excommunication of those who did not accept the takkanot.