Sforno explains the verse “You shall teach them to your children to speak with them when you sit in your house...” to mean that one must teach his children to engage constantly in the words of the Torah—in the morning and at night, and under all circumstances.
On a more literal level, however, one can understand this verse as an instruction to be constantly educating our children—“You shall teach them to your children... when you sit in your house and when you go on the way, when you lie down and when you rise.”
Practically, this means that providing a proper Jewish education to your children—and by extension, to all Jewish children whom you can reach and affect—must constantly be on your mind. You must think about their education, and be active in ensuring it, not only “when you sit in your house”—i.e., when you focus on your family life—but even as you “go on the way”—as you go about your daily affairs. Even when you relax and wind down at the end of the day, your thoughts “when you lie down” to sleep should be about the importance of providing the next generation with a proper Torah education.
Moreover, the verse continues, “You shall teach them to your children... when you rise up.” In the very first moments after you wake up, along with your recitation of Modeh Ani, thanking G‑d for restoring your soul for another day, your first thoughts must be, “How will I best fulfill my duty to teach the Torah to my children today?”
—Sichos Kodesh 5737, vol. 2, pp. 388–389
