Sefer Chasidim (“Book of the Pious”) is an ethical and legal guide to everyday life and a foundational text of Chasidei Ashkenaz, a mystical and ascetic movement that flourished in Germany during the 12th and 13th centuries. The work teaches the righteous how to dress, speak, pray, work, sleep, interact with gentile neighbors, and make life-decisions, like whom to marry and where to live. It puts an emphasis on avoiding honor, wealth, physical pleasure, and extramarital sex, and its legal rulings are generally stringent. Given the ample attention the work devotes to realistic details, it is considered a critical source for studying Jewish civilization in medieval Germany.