Hungarian rabbi; died about 1807. Through the influence of Aaron Chorin, a disciple of his father, he became rabbi of Deutschkreuz, near Mattersdorf, Hungary. He wrote "Ḥen Ṭob" (Zolkiev, 1806), commentary on a part of the code Eben ha-'Ezer, to which is added "Zebed Ṭob," on the same code, by his son-in-law Isaac (Eisik) ben Lippmann Fränkel. Joab wrote also: "Sha'are Binah," novellæ to Isaac ben Reuben Alfasi's "Sha'are Shebu'ot," Vienna, 1792. Like Joseph Caro, Marcus Benedict, and others, Mattersdorf mistook this Isaac ben Reuben for a grandson of Isaac Alfasi (see Jew. Encyc. 1:377, s. ALFASI, ISAAC BEN REUBEN).