The Talmud seeks the biblical source for the father’s obligation to teach his son Torah.

Concerning the father’s obligation to teach his son Torah that is mentioned in the baraita, the Gemara asks: From where in the Torah do we derive it? As it is written: “You shall teach them to your sons to speak of them” (Deuteronomy 11:19). This is the source for the requirement of a father to teach his son Torah.

On the basis of that source, one might conclude that this obligation is incumbent exclusively on the father, and therefore, if the father neglected to do so, the son is exempt from the obligation to study Torah himself. The Gemara explains that this is not the halakha: And in a situation where his father did not teach him, he is obligated to teach himself, as it is written: “And you shall learn them, and you shall take care to perform them” (Deuteronomy 5:1). Consequently, if one’s father did not teach him Torah, he must study Torah on his own.