Explanation #1: Rashi establishes it in connection with separating T'rumah from one species on the other.

Explanation #2: The Ri however, cites the Gemara in Menachos (in Perek Rebbi Yishmael Daf 70.) which in turn, cites a beraisa, from which it is evident that it is written in connection with the Mitzvah of Chalah.

Question: Some commentaries ask from the Mishnah in Chalah (Perek 4, Mishnah 2) 'Wheat does not combine with everything, only with spelt; Whereas barley combines with everything except for wheat.

Question (Concl.): So we see that spelt combines with wheat?

Answer: The Ri answers that, when our Gemara says that 'Spelt is a species of wheat' - it means that it is also a species of wheat, but that it is certainly a species of barley; whereas oats and rye are a species of barley exclusively.

Implied Question: When the Beraisa says there (at the beginning of the Maseches) that the five things that are Chayav Chalah: wheat, barley, spelt, oats and rye all combine with each other?

Answer: The Ri cites the Yerushalmi which answers - 'One speaks Nashuch, and the other, by Balul ...

Explanation: 'Nashuch' means - that each one was kneaded into a separate dough, and then joined by 'cliping them together'; There, to be sure, they do not all combine, only in the manner that is described in our Sugya. Whereas 'Balul' means all the various types of flour were kneaded together into one dough. And it is in such a case that they all combine, since we reckon them as one entity.

Clarification: With regard to being Chayav Kareis, like we say explicitly - 'One is not Chayav Kareis on its Chimutz, but a La'av there is'.

Proof: And likewise we will shortly say that 'One is forbidden to knead with wine oil and honey; and if one did, it must be burned immediately.

Proof (cont.): And even the Chachamim, who allow it to be eaten, that is only because it is possible to guard it against Chimutz; but even they concede that it is subject to Chimutz.

Question: Later on (Daf 40.), regarding the case of 'Kimcha de'Avishuna', the Gemara concludes that fruit-juice is permitted, since fruit-juice is not subject to Chimutz.

Support: And this is also the opinion of Rabeinu Tam, that fruit-juice is not subject to Chimutz at all.

Implied Question: And when it says 'that it must be burned immediately'...

Answer: It is speaking where one mixed in water, in which case it is Machmitz more rapidly. And it is about such a case that the Gemara states that they are not subject to Kareis, only to a La'av.

Answer (cont.): But there where no water has been added, such as wine, vinegar and other fruit-juice (exclusively), are completely permitted.

Proof: And this is evident at the end of 'Kol ha'Menachos Ba'os Matzah' (Menachos Daf 57:) where, citing Rebbi Yossi ha'Gelili, it says "asher takrivu" - 'to include the Minchas Nesachim' in the realm of Chimutz'.

Proof (cont.): But surely, the Gemara asks, the Minchas Nesachim is made with fruit-juice, which is not subject to Chimutz?' To which Resh Lakish, citing Rebbi Yossi, replies ''That if the Minchas Nesachim was mixed with water, it would still remain Kasher'.

Proof (cont.): Now if one would think that Rebbi Yochanan and Resh Lakish here were speaking without water at all, and even then, there is no Kareis, only a La'av, since it is Chametz Nokshah ...

Proof (cont.): Why does the Gemara there see fit to mention 'Megavlah ba'Mayim', since even without water we need the Pasuk of "she'Lo Te'afeh Chametz", seeing as it Chametz Nokshah, and Chametz Nokshah is Pasul for a Minchah?

Proof (cont.): As is implied there in Menachos (Daf 53.) where it explains how the Si'ur of Rebbi Yehudah according to Rebbi Yehudah is Pasul for Menachos.

Proof (concl.): We are therefore forced to say that where there is no water it is not Machmitz at all.

Question: The Rashba asks that, in Perek Eilu Ovrin (Daf 43.) the Gemara considers Chometz ha'Edomi 'a mixture of proper Chametz'. Why is that, seeing as the Gemara there defining 'Chometz ha'Edomi', explains that one throws in barley - meaning that one places barley in wine in order that it should be Machmitz well.

Question (cont.): But (as we just explained) fruit-juice is not Machmitz. And even if one were to add water, it would still only be Chametz Nokshah (and not proper Chametz)?

Answer: The Ri answers that they tended tosoak the barley in water before placing it in the wine.

Rashi's Doubt: Rashi is not sure whether egg-water is considered fruit-juice or not, bearing in mind that, as we see, the dough becomes thicker (when it is used) more than it does when water is used.

Rabeinu Tam's Resolution: Rabeinu Tam however, permitted it...

Ruling: In fact, on Erev Pesach after four hours, he used to eat cake that had been kneaded with egg-water.

Implied Question: And whent the Yerushalmi says that 'Anybody who eats Matzah on Erev Pesach before its time is as if he would have had relations with his betrothed in the house of his in-laws' ...

Answer: It is referring to Matzah that is eligible to fulfil one's obligation.

Answer (concl.): Whereas this is 'Matzah Ashirah' (which cannot be used for Matzos Mitzvah).

The Doubt (Side #1): The Ri is not sure as to whether the Gemara wants to say that one is Yotzei Bedi'eved - as we say 'Since he is able to declare his property Hefker, in which case it will be fit for him'. Nevertheless, he has not yet done that.

The Doubt (Side #2): Or whether one is Yotzei even Lechatchilah, since the poor are permitted to eat it.

Conclusion: And eating Matzah is also called 'the eating of poverty'.

Clarification: The Yerushalmi establishes this by Nochrim.)

Question: If "Kesef" is exclusive, then we ought to preclude anything that is worth money (i.e. anything other than money itself) ...

Question (cont.): Whereas if we learn from "Yashiv" that whatever is worth money is like money, then we ought to include Karka, too?

Answer: The Ri therefore ascribes it to a K'lal u'P'rat u'K'lal: "Veyasaf Chamishis"- K'lal, "Kesef"- P'rat and "Vehayah lo" - K'lal, from which we learn that just as the P'rat is moveable, and is intrinsically Mamon, so too, the K'lal, which precludes Karka'os, Avadim and Sh'taros.

Proof: And this explanation is evident in the Mishnah in Bechoros (Daf 51.) which forbids redeeming with Avadim, Sh'taros, Karka'os or Hekdeshos. The Gemara explains there that Hekdeishos does not belong in that group ...

Proof (cont.): The Gemara there learns B'chor from a K'lal u'P'rat u'K'lal, and we can say the same for Hekdeishos.

Question: Why does the Gemara in Perek ha'Zahav (Bava Metzi'a Daf 54.) ask whether the extra fifth (that one pays when redeeming a Hekdesh field) can be redeemed with Karka, considering that the Chief Miy'ut (precluding Karka) is written in connection with the Chomesh - as the Pasuk writes (in Vayikra 27) "And he shall add a fifth of the money of the Erech" (the Pasuk we cited earlier from which we learn the 'K'lal u'P'rat u'Klal)?