“Lamed means to learn and to teach… The commandment to teach… is a directive for every individual.
The Torah tells us that ‘You shall teach your children and talk to them about these things’ (i.e., the Torah’s commandments and responsibilities)… through the commandment to teach our children, we know of our own obligation to study the Torah. For how can we teach our children the Torah if we haven’t learned it ourselves?
If G-d wanted to tell us that we are obligated to learn Torah, why didn’t He just say, ‘Learn Torah!’
…
When it comes to studying Torah, a person is always a child, and thus the commandment to ‘teach your children’ can also apply to us. One should never say, ‘Oh, I’m fifty now. I’ve read through the Torah more than twenty times’…
On the contrary, Torah is infinite. No matter how many times we’ve set foot in it, we can always discover a new insight or uncover deeper meaning.”