Rabbi Shimon ben Zemach Duran (1361-1444) was a colorful rabbinic authority in Algiers. In his book, 'Zohar Harakia,' on methods of enumerating the 613 commandments, he summarizes the work of previous authorities on this subject, especially Maimonides and Nachmanides. He also presents his own system of enumeration. Thus, his work is a compact introduction to this fundamental subject. The text, first printed in 1515, is written clearly and arranged as a commentary on ibn Gabirol's poetic version of the 613 commandments, which is chanted on Shavuot. This English translation and notes make it accessible to lay readers as well as students of Jewish law, liturgy, and medieval Jewish history.