תּוֹרָה נג - הֵ"א הַדַּעַת

Through striving to draw people close to Hashem Yisborach and to true Tzadikim — through this one merits children. A person must strive to attain the completeness of da'as [knowledge/awareness] — that is, to merit holy da'as to the fullest extent a person can know and attain — beyond which it is impossible for a person to know further. And it is impossible to come to this except through engaging with people to draw them close to the service of Hashem Yisborach. Through this his da'as is completed as above. And through this he merits children — and can restore barren women. And this is the reason that Tzadikim exert themselves and pursue people to draw them close to His service, may He be blessed. For this is not in order to increase their own honour — G-d forbid. Rather: in order to complete their da'as as above.