Sotah Chapter 3, Mishnah 6. This mishnah deals with various cases in which the minchah of the sotah - the meal offering the woman brings - cannot be brought to the point of being offered.
The minchah became tamei:
"Nitma minchasah ad shelo kidshah bichli - harei hi k'chol hamenachos v'tipadeh" - if the minchah became tamei before it was placed into the clay vessel, that is, before it was sanctified, its law is like that of all other menachos and it is redeemed. The reason: at this stage it carries only kedushas damim - its value is sanctified, but its body, the actual physical substance, has not yet become sanctified. Therefore the sanctity of its value can be transferred onto money, and this is what is called redeeming the minchah.
"V'im mishekidshah bichli - harei hi k'chol hamenachos v'tisaref" - if it became tamei after it had already been sanctified in the vessel, its law is like that of all other menachos that became tamei once they were in the clay vessel, and it must be burned.
"V'eilu shemenchoseihen nisrafos":
"Ha'omeres temei'ah ani lo" - a woman who says in the middle of the process: I did indeed become defiled and commit adultery. She is not given the sotah waters to drink, nor is her minchah offered; rather, it is disqualified and must be burned.
"V'sheba'u lah eidim shehi temei'ah" - witnesses came and testified that she committed adultery. Here too she does not drink, and her minchah is not offered but is burned.
"V'omeres eini shosah" - a woman who refuses to drink, and said so before the passage containing Hashem's Name was erased into the water.
"V'sheba'alah eino rotzeh l'hashkosah" - the husband changed his mind and is unwilling to have her drink, after he had already brought the minchah.
"V'sheba'alah ba aleha baderech" - the husband lived with her on their way to the Beis HaMikdash, after the status of a sotah whose adultery is uncertain had already taken effect, at a time when she was forbidden to him. If this became known only after the minchah had already been sanctified in the vessel, this minchah too is burned.
"V'chol hanesu'os l'kohanim minchasan nisrefes":
The menachos of sotos married to kohanim are also burned, and the reason lies in the difference between the minchah of a Yisrael and the minchah of a kohen:
The minchah of a Yisrael: the kohen performs kemitzah, taking a full handful and burning that kometz on the mizbe'ach, and the remainder is eaten by the kohanim.
The minchah of a kohen: there is no kemitzah at all and it is not eaten; rather, all of it is burned.
In the case of a kohen's wife who brings this minchah, a kind of intermediate status arises. On the one hand, kemitzah is performed as with the minchah of a Yisrael, since the law that a kohen's minchah is burned in its entirety was stated regarding a kohen himself; the kohen takes the kometz and burns it on the mizbe'ach. On the other hand, since her husband the kohen has a share in her minchah, the remainder is not eaten. Therefore, after the full kometz has been burned on the mizbe'ach, the remainder is burned - not on the mizbe'ach as with a kohen's minchah, but in the place where the other disqualified menachos are burned.
In summary: this mishnah lists the cases in which the minchah of the sotah is not offered. If it became tamei before it was sanctified in the vessel, it is redeemed, since it carries only kedushas damim; if it became tamei after it was sanctified in the vessel, it is burned. So too the minchah is burned in the case of a woman who says "temei'ah ani lo," one against whom witnesses came, one who says "eini shosah," one whose husband is unwilling to have her drink, and one whose husband lived with her on the way. And finally, in the case of a sotah married to a kohen, kemitzah is performed and the kometz is burned on the mizbe'ach, while the remainder is burned in the place where disqualified menachos are burned.