Rabbi lsaiah ben Abraham haLevi Horowitz was also known as Ha-Shelah ha-Kadosh , ‘the holy Shelah’, which comes from the initials his major work. He was a rabbi, kabbalist, and communal leader born in Prague, but as a youth he moved to Poland with his father, who was his first teacher. He studied there under Solomon b. Judah of Cracow, Meir of Lublin known as the Maharam, and Joshua Falk. He soon gained a reputation among Polish scholars. In 1597 he published his father’s Emek Berakhah with the addition of his own notes in which the influence of Kabbalistic teaching is already discernible. In 1600 he became av bet din of Dubno and in 1602 av bet din and head of the yeshivah of Ostraha. In 1606 he was appointed av bet din of Frankfurt.
After the expulsion of the Jews from Frankfurt in 1614, he returned to his home town, Prague where he became rabbi until 1621 when his wife died. He then moved to Israel and settled in Jerusalem, where he remarried and became the rabbi of the Ashkenazi community. He became active in the strengthening of the Ashkenazi community in the capital and in the expansion of the settlement of Ashkenazim in the country. In 1625 he was imprisoned together with other scholars by the pasha and ransomed for an exorbitant sum. He died in Tiberias where his grave is close to that of the Rambam. His son was Shabbetai Sheftel Horowitz (1590?–1660?).