Led by a thirst for Talmudic knowledge, he undertook in his youth extensive journeys to the prominent yeshivot of Germany and France.
Later on, Isaac returned to Regensberg, and then settled for some time in Vienna, where he held the position of Av Beit Din and rosh yeshiva.
He saw the law compelling Jews to wear the yellow badge put into force in France and he deplored the 1241 pogrom in Frankfurt and the extortions practised upon them by the nobles of Austria.
In the edition of Lipa and Höschel Seder Nezikin is wanting; most of the rest of the work was afterward printed at Jerusalem by J.M.
Isaac explains unknown words in Bohemian (i. e. Czech), his mother tongue, and cites the Jerusalem Talmud, to which he ascribes great authority in halachic decisions.
According to Gross, Isaac's chief importance rests upon the fact that he introduced among the Jewish communities in Slavic lands the study of the Talmud from France and the west of Germany.
Isaac was of a mild and peace-loving character and it was for this reason, perhaps, that he did not participate in the struggle against the study of secular sciences, though an incorrect ritual decision would rouse him to indignant energy.
He carried on a controversy with several rabbis concerning the legal status of a betrothed girl who had been forced by circumstances to adopt Christianity and had afterward returned to Judaism.
He was held in high regard by his pupils, and, like other teachers of the time, was given the title HaKadosh "the Holy" by the Asher ben Jehiel.