Halakhah su Salmi 82:1

The Sages ordained that men pray with a minyan (a quorum of ten adult men) in a synagogue. The Sages teach that the divine Presence dwells wherever ten Jews engage in sacred matters (devarim she-bikdusha), as Scripture states: “Elokim nitzav ba-adat Kel” (“God stands in a godly congregation”; Tehilim 82:1), and ten Jews constitute an “edah” (congregation). Although even when one Jew prays or studies Torah the Shekhina is present, there are nevertheless different gradations, the highest level of which is when ten Jews are engaged in a davar she-bikdusha, for then holiness is revealed in the world (see Berakhot 6a). Based on this, the Sages ordained that all devarim she-bikdusha, that is, enactments that express God’s sanctity publicly, shall be recited in a minyan of ten men. Devarim she-bikdusha encompasses Ḥazarat Ha-shatz, Birkat Kohanim, Barkhu, Kaddish, and Torah reading (Megilla 23b).¹Megilla 23b and Sofrim 10:7 mention the things that must be recited with a minyan. The Sages (Megilla op. cit. and Berakhot 21b) derive from the verse “I shall be sanctified among the Israelites” (Vayikra 22:32) that a davar she-bikidusha shall not be recited among less than ten. Ran (ad loc.) and other Rishonim and Aḥaronim explain that this is a rabbinic law, since the very recitation of these words is of rabbinic origin. Nevertheless, the basic idea of minyan comes from Torah law that governs the sanctification of God’s name (Kiddush Hashem). That is, one is obligated to surrender his life rather than desecrating God’s name by performing a transgression under coercion in the presence of ten Jews (Sanhedrin 74b). It seems that for this purpose, women count toward the ten (though Devar Shmuel (Aboab) §63 and Pitḥei Teshuva YD 157:7 raise doubts about this).

And from the laws of the commandment is that which they, may their memory be blessed, said (Shevuot 30a) that it not be that one stand and one sit, but rather both of them stand. As in that they are in front of the court, it is fitting for them to stand as if they were in front of the Divine Presence; since the spirit of God dwells among the congregation of the judges of Israel, as it is stated (Psalms 82a), "God stands in the congregation of God." And nonetheless, they, may their memory be blessed, said (Shevuot 30b) that if they wanted to seat the litigants, the option is in their hand. And about what are these words speaking? At the time of give and take. But at the time of the final judgement, there is an obligation to stand, as it is stated (Exodus 18:13), "and the people stood over Moshe." Except that all of the courts of Israel after the Talmud have become accustomed to seat them [in order to avoid] controversy. And even [regarding] the witnesses about whom it is written (Deuteronomy 19:17), "and the two men stand," they have also become accustomed today to seat them (Mishneh Torah, Laws of The Sanhedrin and the Penalties within their Jurisdiction 21:5). [This] and the rest of its details are elucidated in [various] places in Sanhedrin and Shevuot (see Tur, Choshen Mishpat 17).