Mishpatim תרמ"ה 4

בפסוק וישלח כו' נערי בני ישראל פרש"י הבכורות.

On the verse "And he sent… the young men (na'arei) of Bnei Yisrael" (Shemos 24:5), Rashi explains: these were the firstborn (bechoros).

At the covenant before Matan Torah, Moshe sent "the young men" to bring the offerings. Rashi identifies these na'arim as the firstborn, who served before the Kohanim were appointed.

ויש להבין למה נק' נערי.

And one must understand why they are called "na'arei" (young men).

The Sefas Emes raises a difficulty: if these were the firstborn, why does the Torah describe them with the word for youths?

הלא עפ"י הרוב הבכורות המה זקנים יותר מאחיהם שנולדו אח"כ.

For generally the firstborn are older than their siblings who were born afterward.

The question sharpens: firstborns are by definition the eldest among their brothers, so the term "young men" seems incongruous.

אך הענין הוא כי הבכורות יש בהם כח ההתחדשות ונקראו נערי.

But the matter is that the firstborn possess the power of renewal (hischadshus), and so they are called "na'arei."

The word "na'ar" denotes not chronological youth but the inner power of renewal and freshness. The firstborn embody this energy of beginning anew — the vitality of the first fruit of a person's strength.

ולכן המה מיוחדים לעבודת השי"ת.

And therefore they are designated for the avodah of Hashem Yisbarach.

Because they carry this power of constant renewal, the firstborn were uniquely fit to serve Hashem — for true avodah requires the freshness of always beginning anew.

וכן בבני ישראל נאמר נער ישראל דכתיב בני בכורי שהם דבקים תמיד בשורש ההתחדשות:

And likewise concerning Bnei Yisrael it is said, "Israel is a na'ar (youth)" (Hoshea 11:1), as it is written, "My firstborn son" (Shemos 4:22) — for they are always cleaving to the root of renewal.

Bnei Yisrael as a whole are called both "na'ar" and Hashem's "firstborn," because their essence is to remain eternally bound to the source of renewal — never growing old or stale in their avodah, but constantly drawing fresh vitality from Hashem.

Summary: The firstborn are called "na'arei" not because of their age but because they embody the power of hischadshus — constant renewal. This is why they were chosen for the avodah of Hashem, and why Bnei Yisrael, called both "na'ar" and Hashem's "firstborn," are forever cleaving to the root of renewal.