https://www.chabad.org/library/article_cdo/aid/137084/jewish/Lamed.htm
Lamed (ל) is the twelfth letter of the Hebrew alphabet
Numerical value: 30
Sound: “L”
Meaning: 1. learn 2. teach
Design
The twelfth letter of the aleph-bet is the lamed. The design of the lamed is two letters merged together1: the vav and the kaf.2 The _Kabbalah_3 says that the letter lamed is compared to a tower flying in the air.
Gematria
The gematria of lamed is 30. Ethics of the Fathers tells: “When one reaches the age of thirty, he reaches the age of full strength.”4
What was the underlying purpose of the Jews’ journeying 40 years in the desert? On one hand, we know that it was the result of the sin of the Spies—their negative report after their 40-day scouting mission is what evoked G‑d’s decree that the Jews must remain in the desert for 40 years.5 But why did they specifically have to wander through the desert? Why not stay in one place? Set up camp and stay there for 40 years! What was the reason for having to undertake a total of 42 different journeys in 40 years?
The purpose of the Jewish people’s travels was to transform the desert into a garden; to bring G‑dliness to a desolate place. By carrying the Holy Ark—and within it the Torah—each and every one of the Jews’ encampments became not only a spiritual but a literal garden. This became a lesson and guidepost for the Jewish people in all their future exiles. G‑d was informing them: Throughout history, you will have to travel. You’ll trek from country to country to country. But wherever you go, you must take the Ark of G‑d with you—ushering G‑dliness to that area, elevating it and making its inhabitants more refined and spiritual. This is the purpose of a Jew.6
This power to begin transforming the world in earnest begins when we turn 30. Up until that point, we are in training. The _Midrash Shmuel_7 states that one has the ability to guide and influence others for good at the age of 30. Until then, he is simply laying his foundation.
We find another interesting gematria in relation to lamed. Both the aleph (in the form of the word ulfana) and the lamed (as in lameid) represent G‑d as a teacher. What’s the connection between the two letters? The aleph comprises two yuds and a vav: 10 and 10 and 6=26. The lamed comprises a kaf and a vav: 20 and 6=26. Twenty-six is the gematria of G‑d’s name, the Tetragrammaton Yud-Hei-Vav-Hei.
We find another interesting gematria in relation to lamed. Both the aleph (in the form of the word ulfana) and the lamed (as in lameid) represent G‑d as a teacher. What’s the connection between the two letters? The aleph comprises two yuds and a vav: 10 and 10 and 6=26. The lamed comprises a kaf and a vav: 20 and 6=26. Twenty-six is the gematria of G‑d’s name, the Tetragrammaton Yud-Hei-Vav-Hei.
This is perhaps why the Zohar refers to the lamed as a tower flying in the air. The vav of the lamed represents G‑dliness, spirituality, found high up “in the air.” The vav, which is a chute, draws this G‑dliness down from the spiritual realms into the physical world, until it is internalized into the kaf, the human being. This merging of spiritual and physical imbues the lamed with the ability to teach lofty concepts in a practical way.
Meaning
Lamed means to learn and to teach—found in the daily prayers with the phrase lilmod u’lelameid.10 But the word lamed, the commandment to teach, is not directed merely toward school teachers, it is a directive for every individual.
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 50 now. I’ve read through the Torah more than 20 times; you can’t teach me anything new.” 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. We must approach it like children and be ready to receive and listen. As we read in Ethics of the Fathers:13 “Who is wise? One who learns from everyone.”