About Bar/Bat Mitzvah
Many people are surprised to find out that "becoming bar/bat mitzvah" happens automatically when a Jewish boy reaches the age of 13 and or a girl 12. The ceremony that today occupies center stage is actually a historical afterthought, with evidence of observance only from sometime between the 14th and 16th centuries. Because the ceremony marks reaching the age of majority, many traditional Jews observe it on the Sabbath immediately following the child's birthday.
For the rabbis, the significance of this life-changing moment lay in the child's new stage of physical, intellectual, and moral development. They saw 12 and 13 as the ages at which girls and boys, respectively, were no longer entirely subject to impulse, but were beginning to develop a conscience. The term bar/bat mitzvah--which means "obligated to perform the Jewish mitzvot (commandments)"--reflects the child's newfound capabilities and responsibilities.
Although the ceremony that communally affirms the child's coming of age is medieval in origin, there is evidence in rabbinic literature that the father may have recited a blessing when the child reached the age of majority. This blessing, called baruch she'p'tarani, thanks God for freeing the father from responsibility for the child's behavior, signaling a transition of control and hence responsibility from parent to child
Development of the Bar/Bat Mitzvah
The relatively late development of the bar mitzvah ceremony probably derives from changes in communal customs regarding what ritual activities a child was allowed to perform. According to the Talmud, which was completed around the sixth century CE, boys were permitted to perform many ritual acts, for example, donning tefillin (phylacteries), whenever they had developed the necessary expertise and were able to understand the ritual's significance. Later this window of opportunity closed, and children were not allowed to perform these rituals until they had reached the age of majority. At this point, a ceremony celebrating the first performance of these rituals began to make sense.