R. Eliezer of Metz

R. Eliezer ben Shmuel of Metz (c. 1115-1198), known as the Re'em (acronym of Rabbenu Eliezer MiMetz), was one of the leading first-generation Tosafists and the leading talmid of Rabbenu Tam. His Sefer Yereim ('Book of the God-fearing') is among the earliest and most influential of the Ashkenazi sifrei mitzvot — a systematic topical exposition of the 613 commandments organized around their underlying theological motivations (fear of Heaven, love of God, social ethics, etc.). The work is widely cited throughout the Tosafists, the Mordechai, and the later Acharonim.