Parents must train their children to fulfill the mitzvot and to study Torah from a young age. If they fail to develop good habits in their youth, it will be very hard to teach them later.

The Sages taught: A minor who knows how to wave the lulav on Sukkot is obligated in the mitzva of lulav; a young boy who knows how to wrap himself in a garment is obligated in the mitzva of ritual fringes; if he knows to preserve the sanctity of tefillin [in a state of bodily cleanliness], his father buys him tefillin; when he knows how to speak, his father teaches him Torah and Shema. What is the Torah that his father teaches him first? Rav Hamnuna said: “Moses commanded us the Torah, a heritage of the assembly of Jacob” (Deuteronomy 33:4). And what is the Shema that his father teaches him? The first verse of Shema.

“Educate the lad in accordance with his way” (Proverbs 22:6). Rabbi Eliezer and Rabbi Yehoshua each interpreted this verse. Rabbi Eliezer said: If you educate your son in matters of Torah while he is a lad, he will mature with them as his guide, as it is stated: “Even when he grows old, he will not turn from it” (Proverbs 22:6). And Rabbi Yehoshua said: It is like an ox that did not learn to plow, and therefore it ultimately finds plowing difficult; or like a vine branch, which if you do not bend it when it is moist, you will not succeed in bending it when it is rigid. (Sukka 42a; Midrash Mishlei [Buber] 22)