Parashas Vaeira
וַיִּקַּ֨ח אַהֲרֹ֜ן אֶת־אֱלִישֶׁ֧בַע בַּת־עַמִּינָדָ֛ב אֲח֥וֹת נַחְשׁ֖וֹן ל֣וֹ לְאִשָּׁ֑ה וַתֵּ֣לֶד ל֗וֹ אֶת־נָדָב֙ וְאֶת־אֲבִיה֔וּא אֶת־אֶלְעָזָ֖ר וְאֶת־אִֽיתָמָֽר׃
Aaron took to wife Elisheba, daughter of Amminadab and sister of Nahshon, and she bore him Nadab and Abihu, Eleazar and Ithamar.
Torah Temimah points to R’ Elazar — Bava Basra 110a (verified).
בת עמינדב — א״ר אלעזר: לעולם ידבק אדם בטובים, שהרי משה שנשא את בת יתרו יצא ממנו יהונתן\ldots ואהרן שנשא את בת עמינדב יצא ממנו פינחס.
English: “Daughter of Aminadav” — R’ Elazar said: A person should always attach himself to the good, for Moshe who married the daughter of Yisro produced from him Yehonasan\ldots while Aharon who married the daughter of Aminadav produced from him Pinchas.
Custom
Chazal teach that one should cleave to the good, illustrated by the differing descendants of Moshe’s and Aharon’s marriages.