Mussar מוסר

The word mussar appears already in Mishlei and means instruction or discipline. As a genre it dates from the rishonim: Duties of the Heart by Rabbeinu Bachya, Gates of Repentance by Rabbeinu Yona, Mesilat Yesharim by the Ramchal—books about inner obligations rather than outward acts.

As a movement it began in Lithuania in the mid-nineteenth century. Rabbi Yisrael Salanter saw the gap: people strict about kashrut and careless about honesty, who knew a tractate by heart and could not restrain anger. He proposed a method—reading short passages aloud, in a melody, at dusk, and examining one's own conduct.

Yeshivot resisted at first, holding that mussar took time from Gemara. In time a mashgiach appeared in the Lithuanian yeshivot—a mentor responsible for the person rather than the learning.