Judah ben Samuel settles in Regensburg, where he founds a yeshiva (academy) and gathers such disciples as the mystic angelologist Eleazar ben Judah of Worms (also a member of the Kalonymos family) and the codifiers Isaac ben Moses of Vienna and Baruch ben Samuel of Mainz.

A founder of the fervent, ultrapious movement of German Hasidism, Judah is also the principal author of the ethical treatise Sefer Hasidim.

(Published in Bologna in 1538, it is possibly the most important extant document of medieval Judaism and a major work of Jewish literature.)

The leaders of the movement are Samuel ben Kalonymos, the Hasid; his son, the semilegendary pietist Judah ben Samuel, the Hasid of Regensburg; and Eleazar ben Judah.

Judah ben Samuel, the son of Samuel the Hasid, also a mystic, belongs to the eminent Kalonymos family, which provides medieval Germany with many of her Jewish mystics and spiritual leaders.

The Kalonymos family had migrated from Italy imbued with knowledge of occultism and versed in Kabbalistic traditions connected with the mystical contemplation of "the throne of God” (merkava, literally, chariot; Ezekial 1).

Efforts to experience the mystical presence of God, however, are based on humility and love of God rather than on merkava-like visions.

He leaves Speyer for Regensburg in about 1195, possibly because of German persecution.