One of the confusing gemara that came up on the daf over peasch was about heitar mitzarsef le'isur: [the next paragraph is just a summary, the way I understand it, you can't skip it]
Rabbi Yochanan says only by nazir does permitted stuff join to asur stuff. (bottom 35b) then: Rav Dimi recited the above teachings. Abaye questioned him about a case of chulin cereal with trumah spices which the mishnah says if touched by a tevul Yom is tameh for that specific part of the cereal, Rabbi Yochanan explained that by saying it's fully trumah so even a non-cohen would be given lashes for eating it(since it's so much trumah; it's pasul from the touch of a tovel Yom) from here abaye sees that the chulin cereal is joined to the asur spices. Rav dimi answers that a non-kohen is only lashed for eating a kezayi of spices(not cereal) in a kedi achilat pras.
Here's where I got stuck: the gemara asks- Does the Torah really obligate one for eating a k'Zayis (of Isur) bi'Chedei Achilas Pras?-[ I know the gemara responds that kedi achilat pras actually is biblical but I am confused as to what the question and seemingly simple answer on Rav dimi is] my question is: what is the alternative- if the span of kedi achilat pras is not from the Torah then how long do you have to eat it in order to be lashed for eating trumah on a biblical level???
I came up with two ideas:
1) the Torah didn't specify a time limit for the isur of eating in general and the Rabbi are the ones who establish it as begin a kedi achilat pras. Then my question is what does it matter that the Rabbi picked the time, shouldn't he get biblical malkot anyway? Otherwise(if you don't ratify the Rabbi's time limit to a biblical level) can you ever get malkot for eating something???
2) maybe to be chayiv on a Torah level you need to eat the kezayit of trumah immediately and without interruption after you begin. The rabbis are the ones adding the limit of kedi achilat pras in order to be chiyuv. The implication is: If one eats a kezayit of trumah spices mixed throughout a cereal you'll only be chiyuv on a rabbinic level not enough for lashes but biblically nothing happened wrong [does this mean that for eating any biblical obligation such as matzah, you have to eat it in a gulp, not even 3 min]. According to this abaye asks Rav dimi how can Rabbi Yochanan propose that he gets lashes for eating a cereal of trumah spices if he's not eating it straight?
My question is not so clear, but I tried my best.
Ike Sultan, west orange, NJ
The key here is whether one eats the forbidden food on its own or in a mixture. The Gemara thought that according to Abaye one is only culpable if one eats the Isur without anything mixed in with it. Then, even if one ate a k'Zayis of Isur b'Kedei Achilas Pras nevertheless since it was in a mixture one would be exempt. However if one eats the Isur without anything being mixed in with it, the Gemara agrees all along that one is Chayav, and the time limit for eating it would be k'Zayis b'Kedei Achilas Pras.
[According to this way of thinking if one eats a k'Zayis of Matzah in 2 minutes - the most stringent opinion - one certainly performed the Mitzvah. However if the matzah was mixed in with something else you might be getting yourself into a problem even if you ate the k'Zayis of Matzah, together with additional accompaniments, within an Achilas Pras.]
The above is stated by Tosfos 36b DH uk'Zayis who writes that since the Isur is mixed in, and we do not maintain Heter Mitzaref l'Isur at this stage, the Isur would be Batel (nullified) against the permitted food (see the Arzei Levanon in the name of Keren Orah who explains the following words of Tosfos which are somewhat misleading otherwise).