And the boys grew (Gen. 25:27).
Rabbi Pinhas said in Rabbi Levi's name: They were like myrtle and a wild rosebush growing side by side; when they attained to maturity, one yielded its fragrance and the other its thorns. So for thirteen years both went to school and came home from school. After this age, one went to the house of study and the other to idolatrous shrines. Rabbi Eleazar ben Rabbi Shimon said: A man is responsible for his son until the age of thirteen; thereafter he must say, "Blessed is He who has now freed me from responsibility for this boy." (Gen. R. 63:9)
Rather astoundingly, this is one of the earliest mentions of what would, over millennia, become the bar/bat mitzvah. Besides equally ancient sources referring to the age of "thirteen and one day" as the age at which boys become obligated to perform religious duties, Rabbi Eleazar ben Shimon's teaching is all we have until the Middle Ages on which to hang our treasured life-cycle ritual.
The bar/bat mitzvah ritual has in our day come to be the moment at which parents stand back and beam at the product of their decade-plus of child rearing. How fitting, then, that the rite should find its roots in the tale of Jacob and Esau, twins reared by the same parents. In telling their story, the Torah gives us no clear answer vis-à-vis the nature-versus-nurture debate. The natures of Jacob and Esau are described from the womb as deeply contentious and, as the boys grow, we see Esau grow to be a "skilled hunter," while Jacob "stayed in camp." On the nurture side is the painful verse 28, "Isaac favored Esau because he had a taste for game; but Rebekah favored Jacob."
This midrash brings us back to the question at the heart of every parenting endeavor: What makes one child turn out to be fragrant myrtle, and the other a wild rosebush full of thorns? And at what point do we as parents relinquish responsibility for the actions of our children?