Maaser Sheni, Chapter 3, Mishnah 12. The question this mishnah addresses is the status of the vessels that hold maaser sheni: when a person places maaser sheni into vessels, do the vessels themselves become maaser sheni or not?
"HaMash'il kankanim l'maaser sheni":
A person owns jugs that have no connection whatsoever to maaser sheni, and he wishes to put wine of maaser sheni into them, so he says: I am lending these jugs for the needs of maaser sheni. He is not giving them to the maaser and he does not treat them as maaser; he is only lending them for use. About this the mishnah says: "Af al pi shegafan, lo kanah maaser" - even though he sealed the maaser sheni wine inside the jugs, so that they stand sealed, and one might have thought that they had become literally one entity with the wine, the maaser did not acquire the jugs. They do not belong to the maaser, and therefore when he redeems the maaser sheni wine he does not need to redeem the value of the jugs; they remain chullin and not maaser.
He poured maaser sheni into them without specifying:
A person who poured maaser sheni into jugs without establishing whether he is lending them for the needs of maaser sheni or whether they are permanently bound up with the maaser, but simply put the wine into them without specifying - here the mishnah distinguishes between two situations:
"Ad shelo gafan, lo kanah maaser" - if he designated this wine as maaser sheni before he sealed the jug, the status of maaser does not take effect on the jug itself.
"Mishegafan, kanah maaser" - if he had already sealed the jug, and only afterward said that the wine in this jug should be maaser sheni for other produce or for other wine in his possession, the status of maaser sheni takes effect not only on the wine but on the jug itself as well, and when he redeems the maaser sheni wine he must also redeem the value of the jug.
Further laws that depend on the sealing of the jugs:
Since the mishnah is dealing with the status of the jugs before they are sealed and after they are sealed, it adds further laws that relate to the sealing of jugs:
"Ad shelo gafan, olos b'echad u'meah" - when the jugs contain not maaser sheni wine but Terumah wine, and the law is that Terumah is nullified in a ratio of one to a hundred: as long as the jugs are not sealed, one jug of Terumah can be nullified among a hundred jugs (or ninety nine, depending on the opinion) of chullin.
"U'mishegafan" - once they have been sealed, the jug is considered an item of significance, and therefore "uv'chol shehen" - even the smallest quantity is not nullified, and the status of Terumah takes effect on all the jugs, even if there is one in a hundred or more.
"Ad shelo gafan, torem me'achas al hakol" - one who has before him a group of jugs of tevel wine, from which Terumos and maasros have not been separated, may separate Terumah from one jug for all the rest of the jugs, as long as they are all unsealed.
"U'mishegafan, torem mikol achas v'achas" - once he has sealed them, they are no longer considered joined together, and he must separate Terumah from each and every jug on its own.
In summary: In this mishnah we learned that one who lends jugs for maaser sheni - even though he sealed them, the maaser did not acquire them, and the jugs remain chullin. If he poured into them without specifying: if he designated the wine as maaser before sealing, the maaser did not acquire them; and if after sealing, the maaser did acquire them and he must redeem the value of the jug as well. We also learned two additional laws that depend on sealing: before sealing, Terumah is nullified in one hundred, and after sealing it is not nullified even in the smallest quantity; and before sealing one separates Terumah from one jug for all of them, while after sealing one separates from each and every jug.