Maharil—Rabbi Jacob ben Moses Moellin מהרי"ל — רבי יעקב בן משה מולין

Born at Mainz about 1360, he studied in Austria, returned to Mainz and set up a yeshiva there from which the next generation of German rabbis came. He died at Worms in 1427.

He was not only a halakhist but a cantor—and he held that a community's melodies must not be changed: as they were sung, so they are to be sung. The Niggunei Maharil were remembered at Mainz into modern times. From this comes his chief trait as a decisor: custom, for him, is not a preference but an obligation.

His years fell in the Hussite wars and the exactions and massacres that came with them; he dealt with these as head of the communities, not only as a scholar, and his rulings show law and what a community can bear brought together.

He wrote no book of his own. His rulings and customs were recorded year by year by his student Rabbi Zalman of St. Goar; out of those notes came the Sefer Maharil. His responsa were printed at Venice in 1549, the book of customs in 1556. The Rema took nearly all its customs into his glosses on the Shulchan Aruch—and so present-day Ashkenazi practice descends in very large measure from him.