80. Hilchos Talmud Torah

Talmud Torah 1:1

Women, slaves, and minors are not obligated in the mitzvah of Torah study. Nevertheless, a father is obligated to teach his son Torah while he is still a minor, as per Deuteronomy 11:19, “You shall teach them to your sons, to speak about them.” A woman is not required to teach her son Torah because only those who are obligated in Torah study are required to teach it.

Talmud Torah 1:2

Just as a man is required to teach his son Torah, he is likewise obligated to teach his grandson, as per Deuteronomy 4:9, “You shall teach them to your sons and your grandsons.” This mitzvah is not limited to one's children and grandchildren. There is a mitzvah for every wise man to teach all students even if they are not his children. Deuteronomy 6:7 says, “You shall teach them to your sons....” Our oral tradition explains that “sons” here means students, who are also called sons, as we see in II Kings 2:3, “And the sons of the prophets went forth….”

If one is required to teach all students, why does the Torah single out a person's son and grandson? This gives teaching one's son priority over teaching one's grandson, and teaching one's grandson priority over teaching someone else’s son.