An animal can be offered as a sacrifice only if it is permissible food for Jews. A source for this rule is a passage in the prophecy of Yechezkel that speaks of the contribution that will be given by the nation to the nasi Mashiach as a sacrifice to inaugurate the third Beit Hamikdash.

"One lamb out of the flock, out of two hundred, out of the mashkeh of Israel" (Yechezkel 45:15).

While the literal translation of "mashkeh" indicates that the animal should be of the choicest quality, our Sages interpreted it as referring to what is suitable for the meal of the people of Israel, i.e. permissible for them to eat. This rules out a treifa, an animal suffering from a terminal condition that is forbidden as food.

The question arises, however, why it is necessary to draw upon this source when we already have another one. In commanding Jews to tithe heir herds and flocks and offer the tenth one as a sacrifice the Torah describes these tithed animals as "whatever passes under the rod" (Vayikra 27:32). Since the treifa cannot wholesomely pass under the rod that is carrying out the tithing, it is eliminated as a candidate for sacrifice.

The gemaras resolution is that both sources are necessary to rule out the treifa as a sacrifice. The passage in Yechezkel which mentions the figure of two hundred is interpreted as hinting at the rule that if a forbidden ingredient such as the wine from grapes that grew in the first three years of their vines (orlah) fall into kosher wine to be used for a libation on the altar it is eliminated as a problem if there is 200 times as much of the kosher substance. Since one part of this passage deals with orlah which never had a status of being permissible we must assume that the treifa ruled out as a sacrifice is also one who was born with that defect and was never eligible to serve as a sacrifice. It is therefore necessary to have the second source to teach us that even if it became a treifa at a later stage and was once eligible it is ruled out as a sacrifice once it becomes a treifa which cannot "pass under the rod".

When a mincha flour offering was brought in the Beit Hamikdash the Torah commanded the kohen performing the service to take a three-finger full kometz mixed with oil "and all the levona incense which is on the mincha" and place it on the altar to be burned" (Vayikra 6:8).

There are a couple of issues raised by the need to include levona in this offering.

First of all there is the practical problem of properly performing the act of kemitza removal of the kometz while there is levona incense on top of the flour batch. The Mishna (Menachot 6a) states that if even a grain of the levona was gathered up with the flour in the kometz it is disqualified because it is not an absolutely full measure. If so, how was it possible to make kemitza and avoid levona getting in the way?

Rashi solves this problem (ibid. 11a) by pointing out that the levona was all pushed to one side of the vessel containing the flour so that an unobstructed kemitza could be performed in the middle of it.

The other issue is how much of the levona must still be around when it is placed on the altar together with the kometz. There are three different opinions on this point, all of them based on varying interpretations of the above-mentioned passage.

Rabbi Meir sees in the Torahs phrasing regarding "all the levona which is on the mincha" an absolute need for all of the levona to remain when offered on the altar, the same quantity which it had when it was first placed on the mincha a full kometz of incense. Rabbi Yehuda and Rabbi Shimon, however, interpret the word "kol" in that passage not as all but rather as any, indicating that even if most of the levona is not around, the barest remainder is sufficient. They only disagree as to whether we read into the word "ess", which we literally translate as "and", a message to require more than the absolute minimum of one grain of levona. Rabbi Yehuda sees this "ess" as adding one more grain to the minimum level of "kol" and therefore requires a remainder of two grains, while Rabbi Shimon maintains that even one grain is enough.