Menachos, Chapter 3, Mishnah 1. This mishnah sums up the topic of disqualifying intentions. As we have seen throughout the previous chapters, there are four primary services in a minchah:
The kemitzah - taking a handful from the minchah.
Placing it in a vessel - putting the handful into a service vessel, a sanctified vessel.
Carrying it - bringing it to the altar.
The burning - burning that portion on the altar.
If, during one of these four services, certain thoughts entered the person's mind, and in particular thoughts of outside its time or outside its place - that is, that he intends the eating by a person or the consumption by the altar to take place beyond the proper time or beyond the proper place - the offering is disqualified. Other mistaken thoughts, even if they are forbidden or bizarre thoughts, have no effect on the validity of the offering.
However, even within the rules of intent of outside its time and outside its place there are limitations, and our mishnah comes to define them and to teach that there are cases in which even these thoughts do not disqualify the offering.
Intending to eat something that is not normally eaten:
The mishnah says: "Hakometz es haminchah le'echol davar she'ein darko le'echol, lehaktir davar she'ein darko lehaktir - kasher" - one who takes the handful from the minchah intending to eat something that is not normally eaten, or to burn something that is not normally burned, it is valid. This ruling applies to each of the four services: kemitzah, placing in a vessel, carrying, and burning. And these are the two cases:
"Le'echol davar she'ein darko le'echol" - to eat something that is not normally eaten: during the service he had a thought of outside its time or outside its place regarding eating something that is not designated for eating at all, such as intending to eat the handful that goes up to the altar, or the frankincense that goes up to the altar, at the invalid time (tomorrow) or in the invalid place (outside the courtyard).
"Lehaktir davar she'ein darko lehaktir" - to burn something that is not normally burned: during the service he intended to burn on the altar something that is not designated for burning, such as burning the remainder, which is meant to be eaten, tomorrow or on an altar outside the courtyard.
In both of these cases "kasher" - the minchah offering remains valid, since such thoughts disqualify only when he thought about eating what is designated to be eaten, or about burning what is designated to be burned.
The dispute between Rabbi Eliezer and the Sages:
"Rabbi Eliezer posel" - Rabbi Eliezer disqualifies: in his view the offering is invalid even in these cases. The source for these disqualifications is the verse "v'im he'achol ye'achel" ("and if it will surely be eaten"), which refers to two forms of eating: the consumption by the altar and the eating by the kohen. According to Rabbi Eliezer, the joining of these two forms of eating in a single verse does not come merely to teach about two separate kinds of eating, but to teach that the two are bound up with one another, to the point that if he thought about eating what is designated for the altar's consumption, or about burning what is designated for the kohen's eating - the offering is disqualified.
The Sages - disagree, and the halachah follows them. The reason the Torah described the altar's consumption in the language of eating is to teach that its measure is the standard measure of eating, a kezayis: it is the volume of an olive from the handful that was burned improperly, or from the frankincense that was burned improperly, that disqualifies.
Less than a kezayis:
The mishnah continues: "Le'echol davar shedarko le'echol, lehaktir davar shedarko lehaktir, pachos mikezayis - kasher" - intending to eat something that is normally eaten, or to burn something that is normally burned, in an amount less than a kezayis, it is valid. Here we are dealing with an intention that is essentially correct: during one of the four services he intended to eat the remainder, which is designated for eating, at the invalid time or in the invalid place; or he intended to burn on the altar the frankincense or the handful, which are designated for burning, in the invalid place or at the invalid time. However, he does not intend to eat all of the remainder or to burn the entire handful, but only part of it, less than the measure of a kezayis.
In this case too the offering is valid. True, the thought was improper and he should not have entertained it, but since it concerned eating or burning less than a kezayis, there is no act of eating here at all. The halachic measure of eating is a kezayis, a halachah given to Moshe at Sinai, and one who eats less than a kezayis has not performed an act called eating - and so it is throughout the entire Torah. Therefore here too, a thought of outside its time or outside its place regarding consumption by the altar or consumption by a person in a quantity less than a kezayis is not called eating, and the offering remains valid.
"Le'echol ka'chatzi zayis, l'haktir ka'chatzi zayis" - to eat half an olive's worth, to burn half an olive's worth:
Finally the Mishnah states: "Le'echol ka'chatzi zayis, l'haktir ka'chatzi zayis - kasher, she'ein achilah v'haktarah mitztarfin" - if he intended to eat half an olive's worth and to burn half an olive's worth, the offering is valid, because eating and burning do not combine. That is, during one of the four services that are indispensable he had in mind half a kezayis that would be eaten in the disqualifying place or at the disqualifying time - the eating of the remainder - and an additional half a kezayis that would be burned in the disqualifying place or at the disqualifying time - the burning of the levonah or the kometz. The offering is valid, because the two thoughts do not combine: the measure of eating by a person and the measure of burning, which is the consumption by the altar, do not join together to form a full kezayis.
It is worth noting that this last statement was already taught explicitly in the first chapter, and one must ask why the Mishnah repeats it here, since we already know that eating and burning do not combine. The answer is that one might have thought that Rabbi Eliezer, who holds at the beginning of the Mishnah that consumption by the altar and consumption by a person are bound up with one another, would say that even a thought about half a kezayis of burning together with half a kezayis of eating at the disqualifying time or in the disqualifying place renders the offering invalid. The Mishnah therefore teaches that even Rabbi Eliezer agrees that they do not combine, and one who intends half a kezayis for eating and half a kezayis for burning - his offering is valid.