במדבר ג׳:א׳-ד׳

ואלה תולדת אהרן ומשה. וְאֵינוֹ מַזְכִּיר אֶלָּא בְנֵי אַהֲרֹן וְנִקְרְאוּ תוֹלְדוֹת מֹשֶׁה, לְפִי שֶׁלִּמְּדָן תּוֹרָה, מְלַמֵּד שֶׁכָּל הַמְלַמֵּד אֶת בֶּן חֲבֵרוֹ תּוֹרָה מַעֲלֶה עָלָיו הַכָּתוּב כְּאִלּוּ יְלָדוֹ (סנהדרין י"ט):

These are the descendants of Aharon and Moshe. [Scripture] mentions only the sons of Aharon, yet they are called the descendants of Moshe — because he taught them Torah. This teaches us that one who teaches another’s son Torah is considered as having procreated him.

ביום דבר ה' את משה. נַעֲשׂוּ אֵלּוּ הַתּוֹלָדוֹת שֶׁלּוֹ, שֶׁלִּמְּדָן מַה שֶּׁלָּמַד מִפִּי הַגְּבוּרָה:

On the day that Adonoy spoke to Moshe They became his descendants, since he taught them what he had learned from the mouth of the Almighty.

על פני אהרן. בְּחַיָּיו:

In the presence [literally “the face”] of Aharon. During his lifetime.