Rabbi Moshe Yitzchak Gewirtzman (or Gvirzman), fondly known as "Reb Itzikel", was born on 12 Tevet 5642 (January 3, 1882) in Gorlice, Galicia, or according to other sources in a small village nearby. He was the son of Rabbi Naftali Elimelech Gewirtzman and Rebbetzin Chana Breindel, and a descendant of Rabbi Elimelech of Lizhensk. His grandfather, Rabbi Avraham Gewirtzman, a disciple of Rabbi Chaim of Sanz, was regarded as a hidden tzaddik. He was named Yitzchak after the Seer of Lublin; the Shinover Rebbe, Rabbi Yechezkel Shraga Halberstam, his grandfather's son-in-law, added the name Moshe.

His family moved to Shinov (Sieniawa) in 5646, and the boy lived almost constantly in the Shinover Rebbe's home. At twelve, in 5654 (1894), he was sent to study in Tarnów under Rabbi Moshe Apter. On Rosh Chodesh Nissan 1899 he married Rachel, daughter of Rav Yissachar Dov HaKohen Glanz. He later settled in Przeworsk (Pshevorsk), Poland, whose name he came to bear: there he kept an open house on Shabbat and festivals, and Chassidim flocked to him.

On Rosh Hashanah 5700 (1939) the Nazis seized Pshevorsk and burned the synagogue; the Jews were expelled the day after Yom Kippur and fled to Soviet-held territory. Reb Itzikel instructed his Chassidim to refuse Soviet citizenship and was exiled to Siberia in June 1940. His son, two of his daughters and their families perished in the Holocaust; only his daughter Alta Bina and her husband, Rabbi Yaakov Leizer, survived. Returning to Poland in 1946, he lived in Breslau and then Krakow before moving to Paris in 1949, to the Pletzl neighborhood.

In 1957 he settled in Antwerp, Belgium, where he served as a Chassidic Rebbe and as president of Kollel Galicia-Chibat Yerushalayim. His teachings, stories and customs were collected in the book Siach Yitzchak, and his life story in Ro'eh Even Yisrael.

He passed away in Antwerp on Yom Kippur, 10 Tishrei 5737 (1976), at the age of ninety-four, after forty-three years of leadership. Tens of thousands attended his funeral. He is buried in the Jewish cemetery of Putte, in the Netherlands, where an ohel was built over his grave. His son-in-law, Rabbi Yaakov Leizer, succeeded him.