(ח) יְהוּדָה בֶן טַבַּאי וְשִׁמְעוֹן בֶּן שָׁטָח קִבְּלוּ מֵהֶם. יְהוּדָה בֶן טַבַּאי אוֹמֵר, אַל תַּעַשׂ עַצְמְךָ כְעוֹרְכֵי הַדַּיָּנִין. וּכְשֶׁיִּהְיוּ בַעֲלֵי דִינִין עוֹמְדִים לְפָנֶיךָ, יִהְיוּ בְעֵינֶיךָ כִרְשָׁעִים. וּכְשֶׁנִּפְטָרִים מִלְּפָנֶיךָ, יִהְיוּ בְעֵינֶיךָ כְזַכָּאִין, כְּשֶׁקִּבְּלוּ עֲלֵיהֶם אֶת הַדִּין:
(8) Judah ben Tabbai and Shimon ben Shetach received [the oral tradition] from them. Judah ben Tabbai said: do not [as a judge] play the part of an advocate; and when the litigants are standing before you, look upon them as if they were [both] guilty; and when they leave your presence, look upon them as if they were [both] innocent, when they have accepted the judgement.
"When judging between ideas, people, or courses of action, consider all sides impartially; do not defend or attack one side or the other. See them both as flawed that you might see the good in each. And when the choice is made, see them both as good that you might remember the flaws in each. In this way you reject nothing even as you choose one thing."
--Rabbi Rami Shapiro, commentary on Pirkei Avot 1:8
אָמַר רַבִּי אַבָּא אָמַר שְׁמוּאֵל: שָׁלֹשׁ שָׁנִים נֶחְלְקוּ בֵּית שַׁמַּאי וּבֵית הִלֵּל, הַלָּלוּ אוֹמְרִים: הֲלָכָה כְּמוֹתֵנוּ, וְהַלָּלוּ אוֹמְרִים: הֲלָכָה כְּמוֹתֵנוּ. יָצְאָה בַּת קוֹל וְאָמְרָה: אֵלּוּ וָאֵלּוּ דִּבְרֵי אֱלֹהִים חַיִּים הֵן, וַהֲלָכָה כְּבֵית הִלֵּל. וְכִי מֵאַחַר שֶׁאֵלּוּ וָאֵלּוּ דִּבְרֵי אֱלֹהִים חַיִּים, מִפְּנֵי מָה זָכוּ בֵּית הִלֵּל לִקְבּוֹעַ הֲלָכָה כְּמוֹתָן? מִפְּנֵי שֶׁנּוֹחִין וַעֲלוּבִין הָיוּ, וְשׁוֹנִין דִּבְרֵיהֶן וְדִבְרֵי בֵּית שַׁמַּאי, וְלֹא עוֹד אֶלָּא שֶׁמַּקְדִּימִין דִּבְרֵי בֵּית שַׁמַּאי לְדִבְרֵיהֶן.
Rabbi Abba said that Shmuel said: For three years Beit Shammai and Beit Hillel disagreed. These said: The halakha is in accordance with our opinion, and these said: The halakha is in accordance with our opinion. Ultimately, a Divine Voice emerged and proclaimed: Both these and those are the words of the living God. However, the halakha is in accordance with the opinion of Beit Hillel.
The Gemara asks: Since both these and those are the words of the living God, why were Beit Hillel privileged to have the halakha established in accordance with their opinion? The reason is that they were agreeable and forbearing, showing restraint when affronted, and when they taught the halakha they would teach both their own statements and the statements of Beit Shammai. Moreover, when they formulated their teachings and cited a dispute, they prioritized the statements of Beit Shammai to their own statements, in deference to Beit Shammai.