Shneur Zalman Fradkin of Lublin (1830–1902), also known as the Toras Chessed (after his main work; תורת חסד "Kindly teaching") or The Liader (after his place of birth), was a famous Chabad posek and gaon.
[1] After marrying, Fradkin traveled to study from Rabbi Eliyahu Yosef of Dribin, where he became a great scholar.
Rabbi Menachem Mendel Schneersohn gave Fradkin an honored position among his followers, calling him a gaon, and having him take part in matters of the Beth din.
The fifth Rebbe of Lubavitch, Rabbi Sholom Dovber Schneersohn, also held Fradkin in high esteem, and said of him, "even in the earlier generations he would have been considered a gaon!"
Fradkin gathered the thousands of his responsa into his monumental work, Toras Chessed, published in two volumes (Warsaw, 1883, Jerusalem, 1909).