Certain portions of the prayer service – specifically, those that fall under the category of "Debarim She'bi'kdusha" (literally, "matters involving sanctity") – must be recited in the presence of a Minyan. If ten men are not present, these prayers may not be recited. These include Nakdishach, Kaddish, Barechu, and the repetition of the Amida. We find different sources for this Halacha – one in the Talmud Babli (Babylonian Talmud), and another in the Talmud Yerushalmi (Jerusalem Talmud). Both sources are based on the Torah's command in the Book of Vayikra (22:32), "Ve'nikdashti Be'toch Beneh Yisrael" – "I shall be declared sacred amidst the Children of Israel." The Talmud Babli notes that the word "Toch" ("amidst") appears also in a different verse – in the story of Korah, when G-d instructed Moshe and Aharon to move away "Mi'toch Ha'eda Ha'zot" – "from amidst this evil congregation" (Bamidbar 16:21). The common word "Toch" establishes a connection between these two verses ("Gezera Shava"). Now the word "Eda" in the second verse appears also in the story of the spies, in which G-d refers to the ten evil spies as "Eda Ha'ra'a Ha'zot" ("this evil congregation" – Bamidbar 14:27) – indicating that the word "Eda" refers specifically to a group of ten people. By extension, then, the command "Ve'nikdashti Be'toch Beneh Yisrael" means that G-d shall be declared sacred among a gathering of ten Jews. Hence, portions of the prayer service which involve declaring the sanctity of Hashem require the presence of a Minyan. Strikingly, it emerges that the source of this Halacha is a group of ten sinners – and not just any sinners, but the ten spies who presented a false, negative report about the Land of Israel, leading the people to reject the land and decide to return to Egypt. Hacham Baruch Ben-Haim would say that the Gemara's inference teaches that all Jews count for a Minyan, regardless of their religious level. The fact that the source of the very concept of Minyan is ten sinful men shows that we do not judge people when they come into the synagogue to determine whether or not they should be counted toward a Minyan. Any Jew who comes and wishes to pray is warmly welcomed, and counted. The Talmud Yerushalmi cites a different source – the Torah's description of Yosef's brothers arriving in Egypt to purchase grain: "Li'shbor Be'toch Ha'ba'im" ("To purchase among those who came" – Bereshit 42:5). There were ten brothers, and thus the word "Be'toch" is associated with the number 10. It thus follows that "Ve'nikdashti Be'toch Beneh Yisrael" refers to a minimum quorum of ten. The Sefer Ha'eshkol (Rav Abraham of Narbonne, 12 th century) offers a third source of this requirement, citing the verse in Tehillim (68:27), "Be'makhelot Barechu Et Hashem" – "Bless G-d in assemblies." The word "Makhelot" stems from the word "Kahal," which refers to a group of ten people. The likely reason underlying this Halacha is the Gemara's teaching in Masechet Sanhedrin (39a) that the Shechina resides in a place where ten or more Jews are assembled. Certain portions of the prayer service are particularly sacred and thus require the Shechina's presence, and so they are recited only when at least ten Jews are in attendance. The portions of the service requiring a Minyan are, as mentioned, referred to as "Debarim She'bi'kdusha," a term which literally denotes "sacred" prayers. If we look at the different sections of the Tefila requiring a Minyan, we find that the common denominator is that they are all interactive. For example, in Nakdishach, Kaddish and Barechu, the congregation responds to the declaration of the Hazan (or, in the case of the mourners' Kaddish, to the mourners). Likewise, the congregation answers "Amen" to the blessings recited by the Hazan during the repetition of the Amida. Also included in this category is Birkat Kohanim, where the congregation listens attentively to the blessing pronounced by the Kohanim and answers "Amen." We may thus conclude that "Debarim She'bi'kdusha" refers to portions of the service that are interactive, and this lends them a uniquely sacred quality. Rav Haim Vital (1543-1620), in Sha'ar Ha'kavanot, writes that the requirement of a Minyan constitutes a Torah law, as evidenced by the fact that the Gemara, as mentioned, infers this Halacha from verses in the Torah. Most Rishonim, however, regarded the Gemara's inference as an "Asmachta" – a subtle allusion in the Biblical text to a law introduced later by the Sages.