The Torah gives us census numbers for the tribes after they left Egypt. Among them, Levi is a standout, with far fewer people than any other tribe. The obvious question is, of course, “why?”
Using the text itself, I have one answer that seems to make sense. When Levi is born, his mother, Leah, says, “’This time my husband will become yilaveh to me, for I have borne him three sons.’ Therefore he was named Levi.”
What does this word mean? Elsewhere in the Torah, it is found in only a few places. Twice it specifically refers to the duties of the Levi:
You shall also associate with yourself your kinsmen the tribe of Levi, your ancestral tribe, to be attached to you and to laveh to you, while you and your sons under your charge are before the Tent of the Pact. (Num. 18:2)
They shall be laveh to you and discharge the duties of the Tent of Meeting, all the service of the Tent; but no outsider shall intrude upon you. (Num. 18:4)
We learn from this that the job of Levi is to be Levi. The name describes their task, their raison d’etre. Levi is because Levi does laveh. So what does the word actually mean? The above suggests some kind of helping or facilitating role, helping the priests fulfill their jobs in building and growing the relationship between G-d and the people.
Another time the word is used in the Torah (besides identifying the tribe itself) it is as follows:
If money you laveh to My people, to the poor among you, do not act toward them as a creditor; exact no interest from them. (Ex. 22:24)
This gives us our meaning. A moneylender is a facilitator, someone who helps someone do what they want to do, without actually being a direct party in the transaction. The bank, for example, may help buy your house, but they do not get to live in it. Instead, the bank facilitates what you already want to do.
In a section of curses, G-d tells us:
The stranger in your midst shall rise above you higher and higher, while you sink lower and lower. He shall be your laveh, but you shall not be his laveh; he shall be the head and you the tail. (Deut. 28:43-44)
Which tells us that a laveh is not a subsidiary role.
In all, we have our definition, the reason for Leah’s name-choice: a Levi is someone who helps others, from a position of leadership or guidance, not as an underling. We can think of numerous comparative words: an escort, or mentor or tutor.
Note the repetition of a theme that is found time and again in the text of the Torah: terrestrial marriages parallel, and even lead, the marriage between the people and G-d. Levi is there to help Leah and Jacob, just as his descendants exist to facilitate and guide the Jewish people in their relationships to G-d.
And in this, we can understand why Levi does not have children at the same rate of other people. Leah named her son in the hopes that Levi’s existence would facilitate her marriage to her husband. And forever more, Levi becomes the person who helps other people with their relationships. Levi becomes the teacher, the guide, and counselor. In the Mishkan, Levi is there to help the people connect with G-d, facilitating and guiding the connection.
The problem with helping other people is that it always comes at a cost. Investing in other peoples’ relationships is that you lack the time and energy to invest as much in your own. And so it proves in Egypt. The tribe of Levi acted in accordance with their name, so they helped other people, but at the cost of their own marriages. Which means they had fewer children while helping the other tribes to have more.