any commandment, ordinance, law, or statute contained in the Torah (first five books of the Bible) and, for that reason, to be observed by all practicing Jews.

The Talmud mentions 613 such mitzvahs, 248 mandatory (mitzwot ʿase) and 365 prohibitive (mitzwot lo taʿase). Many more (some virtually equated with divine law) have been added throughout the ages on the authority of outstanding rabbinical leaders, such as reciting the Hallel (specific psalms) at prescribed times, reading the Book of Esther on Purim, washing the hands before meals, and lighting candles on certain festivals. Though nonobservance of a mitzvah constitutes a transgression (ʿavera), it is understood that not all mitzvahs are of equal importance; circumcision, for instance, is a direct response to a divine command, while the wearing of a skullcap (yarmulke) in public is not. In a broader context, Jews consider all good deeds as the fulfillment of mitzvahs, for such actions express God's will.