Menachos chapter 3, mishnayos 3-5. These mishnayos open a series dealing with a general question: when a single mitzvah is made up of two or more components, does each one hold back the other. The term "me'akev" is difficult to translate; literally it means to hold back, but its intent is that the component is indispensable, and without it there is no way to fulfill the other part.
Our mishnah lists six cases relating to the laws of menachos. The common denominator in all of them: when one component is missing, we do not say that the remaining components stand on their own; rather, everything is void. It is an all or nothing matter.
The six cases in the mishnah:
"HaKometz mi'uto me'akev es rubo" - the kometz must be its full measure, the amount that fits under three fingers or four fingers when the kohen scoops. True, there is the well known principle of "rubo k'kulo" (the majority is like the whole), which applies in many areas of halachah, but here it does not apply: if even a single grain is missing, a tiny amount that causes the kometz not to be full, the missing minority holds back the majority and disqualifies it. Even if ninety nine percent of the kometz was offered on the mizbe'ach, it counts for nothing.
"Ha'isaron mi'uto me'akev es rubo" - as we have learned, in all menachos the minimum measure is at least one isaron, and there are menachos in which the measure is larger, but an isaron is always the absolute minimum. An isaron is a volume of forty three and two tenths eggs; if flour was brought with a volume of forty three and one tenth eggs, that is almost everything but not everything, and it is not enough. That missing tenth of an egg holds back the majority, since it is essential to the remaining part, and the entire minchah is void.
"HaYayin mi'uto me'akev es rubo" - the wine comes together with the menachos when one brings an olah or shelamim, which require a minchas nesachim and accompanying wine. The amount of wine depends on the type of animal being brought:
Goats and sheep in their first year - a quarter of a hin, which is three lugin.
A ram - a third of a hin, which is four lugin (about two liters).
A bull or a cow - half a hin, which is six lugin (about three liters).
If wine was brought and a single drop of the required amount is missing, that missing drop holds back the majority of the wine and prevents it from being valid, since it is essential to it.
"HaShemen mi'uto me'akev es rubo" - the olive oil that comes with the menachos, and nearly all menachos require oil, and its measure is generally a log. If ninety nine percent of the log was brought, it is not enough.
"HaSoles v'hashemen me'akvin zeh es zeh" - the usual components of a minchah are the soles, the flour (generally wheat flour), and the oil, olive oil, and they come as one unit. If one was brought without the other, or the majority of one and all of the other, it counts for nothing. One must bring the full amount of soles and the full amount of oil, and if not - everything is void.
"HaKometz v'halevonah me'akvin zeh es zeh" - when the kohen comes to offer on the mizbe'ach, he takes one kometz from the minchah, and after having pushed the small pieces of levonah aside at the time of the kemitzah, he gathers them back up from atop the minchah, all of them, and the two go up together onto the mizbe'ach. This is a single unit: if he offered the kometz without the levonah or the levonah without the kometz, it counts for nothing, since each of them is essential to completing the other and holds it back.
In summary: this mishnah listed six cases in which the missing component holds back what remains: the kometz, the isaron, the wine and the oil - in which the missing minority holds back the majority and we do not apply "rubo k'kulo"; and the soles together with the oil, and the kometz together with the levonah - in which the two components hold each other back. In all of them the principle is one: any deficiency, even the tiniest, voids the entire minchah.