The Mishna at the end of the 3rd perek, says that one can lend a kohen and separate terumah and sell it to claim back his debt.
But the mishnayos in demay say clearly that one may not sell terumah, because he might come to takoloh before he manages to sell it. For example if he has demay, he can separate all the maasros and keep them himself because hamotzi mechavero, however he must give the terumah to the kohen and he may not sell it, even though it is his by rights..
Avrumi hersh, London england
The only open specific reference to the sale of Teruma I could find is in the Ohr Sameach Hilchos Ma'acholos Asuros Perek 15 Halacho 30 where he states unequivocally that "behold it is permitted to sell Teruma to a Kosher Yisroel in a commercial fashion seeing as it is the property of the Cohane for all intents and purposes". Could you please quote the exact source for the Issur to sell Teruma so that I can answer you accurately. Thanks
Shimon Brodie
I couldn't remember the mekor but someone showed me it's a rashi in sotah on 48a the big Rashi.
Also the tosfos yomtov in the 1st Mishna in demay says this in the name of other rishonim as well.
Terumas maaser of demay may not be sold, it must be gifted regularly for various reasons. One of the reasons is because of takoloh, that you might eat it until you find a buyer.
The Pshat in Rashi in Sotah is to explain why in establishin the Takana of Demai, Chazal chose to require a Chiyuv Nesinah, unlike Ma'aser Rishon and Sheini that the Mafrish keeps the Ma'aser for himself. In the Tosfos Yom Tov in Demai, I found no mention of an Issur Mechira, only a question about what is to be done with the Teruma. He brings the Rambam in 4 places that the Teruma is given to the Cohen, but there is no mention whatsoever of an Issur to sell. On the contrary, The Tosfos Yom Tov follows his words on the Rambam with the 2 shitos, 1) Tosafos who explains that the reason the Teruma is given and not sold is because a) it is a small amount or b) because Teruma has minimal market value.
He also brings a Rash that states openly that one may sell the Terumas Ma'aser of Demai to a Cohain.
B'Mechilah Mi'kvod Toroso, I think that the assumption stated above -"Terumas Maaser of Demai may not be sold, it must be gifted" (or that this Din implies an Issur to sell) - is mistaken.
Shimon Brodie
Acc to Rashi. Why not a chiyiv nesina over here as well dilma mashhi let.
In both places the Takana serves the benefit of the Cohanim. In Demai they get a small amount of Terumas Ma'aser and in Gitten 30 it will be easier for them to get a loan.
Shimon Brodie