Tosefta sur Les Nombres 19:25

There is a stringency with a neveilah (i.e., an animal carcass) that there is not with the waters of purification (Num. 19:9), and [there is a stringency] with the waters of purification that there is not with a neveilah. That a small quantity of the waters of purification is impure, and a small quantity of neveilah is pure. A stringency with neveilah is that the waters of purification purify that which is impure and contaminate that which is pure, but they do not join together impurities, which is not so with neveilah. [Moreover,] the waters of purification that dried out, behold, they are [permanently] pure, [but] a neveilah that dried out, if it is able to be soaked and thus able to return to its former status and join [with an object susceptible to impurity], behold, it is impure.

[With respect to] a storehouse that Jew[s] and Gentiles deposit [their produce] inside, if the majority are Gentiles, it is [considered] certainly untithed, and if the majority are Jew[s], it is [considered] Demai. If it is half and half, it is [considered] certainly untithed, the words of Rabbi Meir. And the Sages say, even if everyone [who deposited produce were] Gentiles, and a single Jew deposits inside it, [all of the produce is considered] Demai. Rabbi Yosei said, in what context does this apply? With respect to a storehouse owned by a private citizen, but with respect to a storehouse owned by kings, we follow after [the rule of] the majority. Rabbi Yehudah said, in what context does this apply? With respect to a storehouse [belonging to] Jew[s] and Gentiles, but [with respect to] a storehouse [belonging to] Jew[s] and Samaritans, we follow after [the rule of] the majority. They said to him, [how can you say that] after you [previously] rendered the ruling on us that, "The storehouses of Yavneh [dating] from before the [Jewish-Roman] War were Demai, [even though] the majority were Samaritans, but a storehouse to which [produce] is taken from outside the Land of Israel into the Land of Israel, such as storehouses of Danab, they are liable [in the laws of Demai], according to the proportion." Rabbi Yehoshua son of Kevisai, said, every day I was reading this passage (Num. 19:19), "The clean person shall sprinkle it upon the unclean person," and I did not understand it, but only in the storehouse of Yavneh [did I come to understand it], and from the storehouse of Yavneh I learned that one pure [person] can sprinkle even onto a hundred impure [people and render them clean].

Said Rabbi Nechemiah, why is everyone trusted as to [the purity of the articles involved in] the purification rite [involving the red heifer] and as to consecrated food ("נאמנין על בהחטאת ועל הקדש", see Lieberman), but not everyone is trusted as to Terumah? So that people will not say, "Behold, I am building an altar for myself," or "Behold, I am burning a red heifer for myself," as it is said (Num. 18:7), "And you (=Aaron) and your sons with you shall safeguard your priesthood in every matter [regarding] the Altar..." (See Chag. 22a:15.) One might say that [the word "safeguard" includes] even [Terumah,] Terumat Ma'aser (the priestly portion taken from a Levite's tithes) and Challah (the portion of dough set aside for the Kohen), [and thus] the Torah comes to teach "... and to [that which is] within the Curtain." What is special about that which is "within the Curtain" is that it is not familiar to [the non-priestly class of] Israelites [who are forbidden from entering the area beyond the Curtain], which thus excludes Terumah and Terumat Ma'aser and Challah, with which Israelites are familiar. Rabbi Yehuda says, behold, it says [in regards to the red heifer] (Num. 19:9), "and it shall be for the congregation of the Children of Israel to safeguard it as the waters of purification...", such that everyone should be trusted as to safeguarding it. [If there is] a doubt as to the status of an am ha'aretz as regards to [the impurity of] treading or movement [of a zav (see Niddah 43a:3)], [they are deemed] pure as to matters of chullin and impure as to matters of Terumah.