It is very important that a person teach his son Torah and guide him in the service of Hashem. This is mentioned several times in the Torah, as it says, ‘and you shall describe to your children and grandchildren the day you stood before Hashem you G-d at Horev’, ‘and you shall teach them diligently to your children’, ‘and you shall teach them to your children to speak in them’, and many other verses. A person should not heed the Evil Inclination’s temptations to take them away from their learning for something more ‘practical’, for we see clearly what happened to those who left Torah for more ‘practical’ endeavors.

And even if the children have already left the heritage of their fathers, one should not be lax in his learning, but should invest extra effort, as it says, ‘if I do not for myself, who will do for me?’