The Rebbe of Lubavitch, Menachem Mendel Schneerson, in a letter dated from Brooklyn, New York, Elul 1, 5711[REF] [1950] writes[REF] about him: "A little while ago, I wrote to the great Rav [Rabbi], distinguished Hassid who fears God, Rav Shmuel Yaakov Rubinstein." .
They knew each other from before the war.