Hebrew name: אבני נזר
Years: 1838–1910
Primary city: Sochaczew
Rabbi Avraham Borenstein was a Polish posek and the first Rebbe of the Sochaczew Chassidic dynasty. Known as the Avnei Nezer after his posthumously published responsa, he also authored the halachic work Eglei Tal. A son-in-law and talmid of Rabbi Menachem Mendel of Kotsk, he established a yeshiva in Sochaczew where he served as rosh yeshiva, creating a unique synthesis of halachic and Chassidic study.