Mordechai Posner (Brother of The Alter Rebbe)

The holy R' Mordechai Posner was a brother of the Alter Rebbe, born to Rabbi Yisroel Baruch Posner and his mother the Rebbetzin Rivka.

The Tzemach Tzedek said of him: "He was a wondrous sharp mind, with a straight and penetrating analytical sense. When he would study a topic he would go through it five or six times, and from one pass to the next he would produce new insights with extraordinary sharpness — like one climbing rung by rung — and his pilpul was delightful and pleasant."

It is told that his facial features closely resembled those of the Alter Rebbe.

The Alter Rebbe appointed him to oversee the study of revealed Torah law (nigleh), and he was one of those responsible for the Chadarim — the Alter Rebbe's inner study circles. Every new student had to be examined by him before being admitted.

R' Mordechai also assisted in proofreading the Shulchan Aruch HaRav.

His family name was Posner — which had also been the Alter Rebbe's family name before he changed it to Boruchovich. R' Mordechai retained the original name, which derives from the city of Pozna from which the Alter Rebbe's family had come.

Several of his responsa are preserved in the Lubavitch library.

Apparently as a consequence of the Napoleonic Wars he was forced to leave Pozna, and in his later years served as rav in the city of Orsha.

On the 11th of Adar, 5583 (March 2, 1823), he passed away, and he is buried in Kapust.

Family

• His son, R' Moshe Ber Posner.
  • His son, R' Schneur Zalman Pevzner.
    • His son, R' Mordechai (Chaim) Pevzner of Klimovichi.
      • His son, R' Shmuel Pevzner.
    • His son, R' Boruch Yaakov Rizberg-Pevzner.
    • His daughter, Mrs. Batya.
  • His son, R' Boruch Tzadok.

Fifth generation

• His daughter, Chana Michla, wife of R' Yisroel Levin (of Nevel).
• His daughter Esther, wife of R' Shlomo Chaim Feldman.
• His daughter Sheina Bashe, wife of R' Yehoshua Zelig Rivkin.