Polish rabbi and author; died in Posen 1685. He was the pupil of R. Jonah Teomim, author of "Ḳiḳayon de-Yonah," and colleague of R. Moses Zacuto; later he became rabbi of Lutzk, Volhynia, whence he went to Grodno. In 1664 he was called to Wilna to succeed R. Moses, author of "Ḥelkat Meḥoḳeḳ"; thence he went (1667) to the rabbinate of Posen. He was called "Rabbi Isaac the Great" because of his extensive knowledge in Talmud and Cabala. He gave his approbation to many books at the meetings of the Polish rabbis. He is mentioned in "Magen Abraham," on Oraḥ Ḥayyim, Nos. 1, 32; and his responsa are found in "Ge'on Ẓebi," "Bet Ya'aḳob," and "Eben ha-Shoham."