Triennial Cycle

The Triennial cycle of Torah reading may refer to the historical practice in ancient Israel by which the entire Torah was read in serial fashion over a three-year period, or to the practice adopted by many Reform, Conservative, Reconstructionist and Renewal congregations starting in the 19th and 20th Century, in which the traditional weekly Torah portions were divided into thirds, and in which one third of each weekly "parashah" of the annual system is read during the appropriate week of the calendar.

There are 54 parashot in the annual cycle, and 141, 154, or 167 parashot in the triennial cycle as practiced in ancient Israel, as evidenced by scriptural references and fragments of recovered text. By the Middle Ages, the annual reading cycle was predominant, although the triennial cycle was still extant at the time, as noted by Jewish figures of the period, such as Benjamin of Tudela and Maimonides. Dating from Maimonides' codification of the parashot in his work Mishneh Torah in the 12th Century CE through the 19th Century, the majority of Jewish communities adhered to the annual cycle.

In the 19th and 20th Centuries, many synagogues in the Reform, Conservative, Reconstructionist and Renewal Jewish movements adopted a triennial system in order to shorten the weekly services and allow additional time for sermons.