R. Mordecai b. Abraham Jaffee (c. 1535–1612), talmudist, kabbalist, and communal leader. Born in Prague, R. Jaffe was sent as a boy to Poland to study under R. Solomon Luria and R. Moses Isserles. There he devoted himself also to the study of astronomy and philosophy (apparently at the instance of R. Isserles). At the same time he studied Kabbalah under R. Mattathias b. Solomon Delacrut. After a few years he returned to Prague, where in 1553 he was appointed head of the yeshivah. Very soon he discovered that the students were not interested in mere understanding of the Talmud but preferred "pilpul" and "were turning the word of the living God into false, corrupt, and evil words" (Preface to his Levush Malkhut). R. Jaffe chose therefore "to minimize the time spent with these students" and applied himself to writing constructive books. He was head of the yeshiva in Prague until 1561, when, by order of the emperor Ferdinand, the Jews were expelled from Bohemia. Jaffe then went to Venice and studied astronomy (1561-71). In 1572 he was elected rabbi of Grodno; in 1588, rabbi of Lublin, where he became one of the leaders of the Council of Four Lands. Later R. Jaffe accepted the rabbinate of Kremenetz. In 1592 he was called as rabbi to Prague; from 1599 until his death he occupied the position of chief rabbi of Posen.