Likutei Moharan 14:4/ליקוטי מוהר"ן י״ד:ד׳

14. This is what our Sages taught: Why do Torah scholars not have sons who are Torah scholars? Because they did not recite the blessing for Torah first (Nedarim 81a). Every person, and especially the Torah scholar, must bless <the Torah first. That is,> through his Torah study, <he must bless> and illuminate the source of the souls—i.e., the “first in thought.” For that is where our source is.

2We find, therefore, when a person brings illumination and blessing into the first thought, and through this the souls shine and are blessed, then when he draws down a soul for his son, he certainly draws a pure and clear soul. As a result, his son will also be a Torah scholar.

3However, when he does not illuminate and bless the “first” through his study of Torah, then, when he draws a soul for his son, this soul is in the aspect of “I am asleep” (Song of Songs 5:2). It does not shine. This is why his son will not be a Torah scholar. And this is: “Because they did not recite the blessing for Torah first”—i.e., the source of the souls, as in, “Israel arose first in thought.”