In his enumeration of all the Biblical commandments (Sefer HaMitzvos, Mitzvah 6), the Rambam describes the mitzvah of learning Torah as “G-d commanded us to study Torah and to teach it.” Learning Torah and teaching Torah are not two separate commandments, according to the Rambam. Rather, you have not fulfilled your obligation to study Torah if you do not teach it. This does not mean that every Jew must work in the teaching profession. But it does mean that every Jew must look for opportunities to share wisdom with others, especially within his or her own family and children.
In most places where the Torah commands and discusses one’s personal Torah learning and study, it is always put in the language of teaching. As we say in the Shema, “You shall teach them to your children and you shall speak of them while you sit in your home and while you walk on the way, when you lie down and when you rise” (Devorim 6:7).
The Sefer Olam HaOsiyos points out that in Hebrew the root of the words for studying and teaching is lamed, mem, daled. Apparently, the act of teaching, melamed, means an eager, intensified learning. Teaching involves a process of heavy learning as well. This is why Taanis 7a says: “Rabi Chanina said: ‘I have learned much from my teachers, from my colleagues even more, but from my students I have learned the most.’” The Torah instructor is really instructing himself as well.
In order to truly study Torah properly, and to genuinely make one’s own studies a meaningful part of one’s life, one must teach Torah to others. The mitzvah is “lilmod u’lelamed – to study and to teach.” As the Mishna (Avos 4:6) tells us: one must be “lilmod al menas lelamed – to learn in order to teach.” The two go hand in hand.
Every generation is a link in the chain from the Revelation at Sinai to modern times. We must receive knowledge from the previous generation and impart that knowledge to the next generation. This is the obligation of Talmud Torah – Torah study. In teaching the next generation, we internalize the information, knowledge, and faith that bring us closer to G-d.
And, as Rav Saadia Gaon said, we ensure that the Jewish people will survive.
