Pesachim 80A

״לא תוכל לזבח את הפסח באחד שעריך״.

“You may not sacrifice the Paschal lamb in any one of your cities” (Deuteronomy 16:5). R' Elazar ben Matya derived from the expression “in any one” that one person cannot be the determining factor in whether the community sacrifices the Paschal lamb in a state of ritual purity or impurity.

רבי שמעון אומר: אפילו שבט אחד טמא ושאר כל השבטים טהורים ⁠— הללו עושין לעצמן והללו עושין לעצמן. מאי טעמא דרבי שמעון, קסבר: שבט אחד איקרי קהל.

R' Shimon says: Even if one tribe is ritually impure and all the rest of the tribes are pure, those tribes who are ritually pure perform the ritual of the Paschal lamb for themselves in a state of purity, and those members of the tribe that is impure perform the ritual of the Paschal lamb for themselves in a state of ritual impurity. The Talmud asks: What is the reason for the opinion of R' Shimon? The Talmud answers: He holds that one tribe is called a community, and a community may sacrifice the Paschal lamb in a state of impurity.

רבי יהודה אומר: אפילו שבט אחד טמא ושאר כל השבטים טהורין ⁠— יעשו בטומאה, שאין קרבן ציבור חלוק. רבי יהודה סבר: שבט אחד איקרי קהל. והוו להו פלגא ופלגא, ואין קרבן ציבור חלוק ⁠— ועבדי כולהו בטומאה.

R' Yehuda says: Even if one tribe is impure and all the rest of the tribes are pure, all the tribes may perform the ritual of the Paschal lamb in a state of ritual impurity, as a communal offering is not divided. The Talmud explains that R' Yehuda holds that one tribe is called a community, and since an entire community is impure, it is considered as though half the Jewish people were pure and half were impure. And a communal offering is not divided. Therefore, all of them may perform the ritual of the Paschal lamb in a state of ritual impurity.