Question: (If a Kav of Chadash and a Kav of Yashan were Noshech each other - R. Yishmael says, he takes from the middle. Chachamim forbid.) R. Yishmael said properly! Spelt and wheat are two species. Since it resembles it, you say that it joins. Chadash and Yashan (resemble each other even more), all the more so!

Answer (R. Heila): Rabanan's reason is, spelt and wheat are two species, and people do not err to say that we may be Torem and tithe from this on this. Chadash and Yashan are one species. If you will say so (he takes from the middle), people will err to say that we may be Torem and tithe from this on this!

(If one takes Chalah from a Kav, R. Akiva says, it is Chalah.) R. Akiva compares this to Peros without final processing. If one transgressed and separated Terumah from them, it is Terumah;

Rabanan compare this to grain that did not grow a third. If one transgressed and separated Terumah from them, it is not Terumah.

Retraction: They retracted to say that it is not like Peros without final processing, and not like grain that did not grow a third;

Rather, R. Akiva compares this to one who says 'this is Terumah on these Peros when they will be detached', and they were detached (it is Terumah). Rabanan compare this to one who says 'this is Terumah on these Peros when they will be detached' (and they were not detached yet).

Assumption: R. Akiva said that one can take Chalah from a Kav - this is from Halachah (a stringency mid'Rabanan), but mid'Oraisa, no.

Rejection: Since it was taught (if there are two Kavim, that Chalah was taken from each by itself...) R. Akiva exempts and Chachamim obligate, this teaches that even mid'Oraisa [R. Akiva says that it is Chalah].

(Mishnah): It turns out that his stringency [causes] his leniency.

Some teach 'his leniency [causes] his stringency.'

The one who teaches 'his stringency [causes] his leniency' refers to R. Akiva, and the one who teaches 'his leniency [causes] his stringency' refers to Rabanan.