Kiddushin, Chapter 2, Mishnah 8. This mishnah deals with a man who betroths a woman with items that carry sanctity: a kohen's portion of the offerings, maaser sheni, and consecrated property. One question underlies all of these cases - is the item used for the betrothal truly the man's own property? For a man can betroth a woman only with something that belongs to him.
Betrothing With One's Portion of the Offerings:
The mishnah opens: "HaMekadesh b'chelko, bein kodshei kodashim bein kodashim kalim - einah mekudeshes" - one who betroths a woman with his portion, whether of the most holy offerings or of the offerings of lesser sanctity, she is not betrothed. A kohen who wishes to betroth a woman with his portion of the offerings does not effect a valid betrothal:
"Kodshei kodashim" - the meat of a sin offering and a guilt offering, which only kohanim are permitted to eat.
"Kodashim kalim" - types of offering meat that may be eaten by anyone.
Either way she is not betrothed, because the kohen is not the owner of these consecrated items. They belong to the Holy One, Blessed is He, and the kohen has merely been granted permission to eat them. Since they are not his money, the betrothal does not take effect.
Betrothing With Maaser Sheni:
Maaser sheni is the tithe that carries sanctity, and it may be eaten only in Jerusalem. The question is whether it belongs to its owner or not, and on this the Tannaim disagree:
Rabbi Meir: "Bein shogeg bein meizid - lo kidesh" - whether unwittingly or deliberately, he has not betrothed her. Whether or not the man knew that he was betrothing her with maaser sheni, the betrothal does not take effect, since maaser sheni is the property of the Most High - it truly belongs to the Holy One, Blessed is He, and a person is granted only permission to eat it. Since it is not considered his, the betrothal does not take hold.
Rabbi Yehudah: "B'shogeg lo kidesh, b'meizid kidesh" - unwittingly he has not betrothed her, deliberately he has betrothed her. Rabbi Yehudah disagrees and holds that this is not the property of the Most High but rather a person's own money. Therefore, if he acted unwittingly, betrothing her without knowing that this was maaser sheni, the betrothal does not take effect - for the woman has no interest in troubling herself to carry it up to Jerusalem, so this turns out to be a mistaken betrothal made on a false premise. But if he acted deliberately, knowing that this was maaser sheni and informing her of it, the betrothal takes effect, since it is his.
Betrothing With Consecrated Property:
Consecrated property does not belong to a person as long as it has not been redeemed, that is, as long as it has not become ordinary property and lost its sanctity. The question is under what circumstances the consecrated item becomes redeemed, since only once it has been redeemed can the betrothal take effect. Here too they disagree:
Rabbi Meir: "B'meizid kidesh u'v'shogeg lo kidesh" - deliberately he has betrothed her, and unwittingly he has not betrothed her. One who betroths a woman with consecrated property while knowing that it is consecrated thereby removes its sanctity, so it is no longer consecrated, and therefore the betrothal takes effect. But when he acts unwittingly the sanctity is not removed, the item remains in its sanctity, and the betrothal does not take effect.
Rabbi Yehudah: "B'shogeg kidesh u'v'meizid lo kidesh" - unwittingly he has betrothed her, and deliberately he has not betrothed her. Rabbi Yehudah holds the reverse: when he acts deliberately the sanctity is not removed, and since the item remains consecrated the betrothal does not take effect; whereas when he acts unwittingly the sanctity is removed and the item becomes ordinary property, and therefore the betrothal takes effect.
In summary: in this mishnah we learned three cases of betrothal with items that carry sanctity. With a kohen's portion of the offerings, whether the most holy offerings or those of lesser sanctity, she is not betrothed, since the meat is not his money and he has been granted only permission to eat it. Regarding maaser sheni, Rabbi Meir holds that it is the property of the Most High and therefore the betrothal does not take effect at all, while Rabbi Yehudah distinguishes between an unwitting case, which is a mistaken betrothal, and a deliberate case, in which the betrothal does take effect. And regarding consecrated property they disagree about when it becomes redeemed and turns into ordinary property: according to Rabbi Meir when he acts deliberately, and according to Rabbi Yehudah when he acts unwittingly - and each of them determines the validity of the betrothal accordingly.