According to Jewish law , when Jewish children reach the age of majority ( generally thirteen years for boys and twelve for girls ) they become responsible for their actions , and `` become a Bar or Bat Mitzvah '' . According to Jewish law , when Jewish children reach 13 years of age for boys and 12 years of age for girls , they become responsible for their actions , and `` become a Bar or Bat Mitzvah '' ( English : Son ( Bar ) or Daughter ( Bat ) of the commandment ) .