Our sages of the Mishnah tell us, in the Ethics of Our Fathers (Pirkei Avot), that the praise of Rabbi Joshua ben Hananiah was "Blessed is He who gave birth to him.".
The commentators explain that the reason Rabbi Joshua praised his mother for being blessed is because his mother took him, even in his cradle, to the house of study so that he would get used to hearing the word of our Holy Torah from a young age.
From this we learn that even children who do not yet have the capacity to understand the words of the Torah, we must teach them to repeat them, either in the form of songs or phrases that, although they apparently do not make any sense (to the child), their soul understands and enjoys them, preparing them so that in the future the words of the Torah will be much easier and more familiar to them.