Related על תרומות 2:1

Rabbi Yosei says, every threshing house is combined into one (see Y. Ter. II.1.11). How is this done? (i.e., how should the threshing house be set up to accomplish this outcome?) One vat for two tanks; two vats for one tank; two vats for two tanks. At a time when everything is combined into one, we take terumah and tithes from one on the other. [If] one of them becomes impure, one takes terumah from the pure that is in it (i.e., in the threshing house) on behalf of the impure that is in it. [If] they are not combined together, one may not take terumah and tithes from one on behalf of the other. [Thus, if] one of them becomes impure, one may not take terumah from the pure that is in it on behalf of the impure that is in it. And similarly, Rabbi Yehudah says, the whole olive press is combined into a single beam. How is this done? One beam for two tanks, two beams for one tank, two beams for two tanks (see Y. Ter. II.1.13). At a time that the whole [olive press] combines as one, we take terumah and tithes from one on behalf of the other. [If] one of them becomes impure we [may] take terumah from the pure on behalf of the impure and tis in it. [If] they are not all combined into one, we may not take terumah and tithes from one on behalf of the other. [Thus, if] one of them becomes impure, one may not take terumah from the pure that is in it on behalf of the impure that is in it.

Rabbi Eliezer says, we [may] take terumah from the pure on behalf of the impure (Ter. 2:1). Said Rabbi Eliezer, it so happened the threshing floors caught fire in Kfar Signah, and they took terumah from the pure on behalf of the impure. They said to him, what proof is that? Rather, [we should conclude] that they took terumah "from them on behalf of them" (i.e., from pure produce on behalf of other pure produce). Rabbi Ilai (אלעאיי not אליעזר per Lieberman) said in the name of Rabbi Eliezer, they [may] take terumah from the pure on behalf of the impure, even [when it comes to produce that is in] liquids. How is this done? Whoever pickles olives in [a state of] impurity and seeks to take terumah from them in purity, he brings a funnel whose mouth is not wider than an egg, and places it on the mouth of an amphora, and brings the olives and puts them inside [the funnel] and takes terumah, and [in this way] he is able to take terumah from the pure on behalf of the impure or the "earmarked" (המוקף, see Tos. Kifshutah). They said to him, nothing is considered "fluid" but wine and oil (see Y. Chal. II.3.9). Rabbi Yosei says, he who takes terumah from the impure on behalf of the pure, whether inadvertent or intentional, his terumah is [valid] terumah (see Y. Ter. VI.1.6). Said Rabbi Yosei, why should there be any difference between this case (i.e., taking terumah from the impure on behalf of the pure) and the case of taking terumah from the bad [quality] on behalf of the good (which is valid terumah (Ter. 2:6 ))?