Rebbe Yehudah Aryeh Leib Alter of Ger (Góra Kalwaria; 1847-1905, Encyclopedia LaChassidut, II, pp. 8-16), second Gerrer Rebbe, an outstanding Chassidic rebbe and Jewish leader in his times. Under his leadership, the Ger Chassidut became the largest and most influential Chassidic dynasty in Poland. He is widely known by the name of his books – the Sefat Emet series on the Torah, the Talmud and other topics.

The Sefat Emet on the Torah is renowned for its depth and originality, and has become a classic Chassidic commentary on the Torah. It is likely the most popular Chassidic book accepted in all Jewish circles, including non-Chassidic communities such as the Lithuanian yeshiva circles and others. The name Sefat Emet was chosen from a verse he cited from Mishlei in his last discourse, a few weeks before his passing.