http://revach.net/article.php?id=2832

Section: Parshas HaShavua   Category: Quick Vort
Parshas VaYeilech: Rav Chaim Kanievsky - It's Talking About The Little Girls
The mitzva of Hakhel requires the attendance of men, women, and children.  The Gemara (Chagiga 3a) comments that we understand why the men and women need to hear the King read the Torah, but why the children?  The Gemara answers that this is to give a reward to the parents for taking them.  Rav Chaim Kanievsky was asked (Derech Sicha) "Why doesn't the Gemara answer that it is because the young boys will soak in the atmosphere of Torah which will enrich their neshamos."  In fact the Yerushalmi says that Rebbi Yehoshua's mother would bring his crib to the Bais Medrash so his ears should hear Torah, proving the power of the words of Torah on little children.

Rav Chaim answered that it is certainly true that the Torah can have a strong impact even on a baby.  In fact in the Gemara (Pesachim 96b) Rebbi Yehoshua says that he once heard a certain halacha regarding Hilchos Temura.  Rav Chaim says that the word says that this is a Halacha he heard in his crib in the Bais Medrash!  "Therefore," Rav Chaim answers, "the Gemara's question is not on the boys.  They have good reason to go.  Rather, the question is on the little girls who must also come to Hakhel."