We just cited Rav Nachman, who rules that both 'Amanah Hayu Devareinu' and 'Moda'a Hayu Devareinu' are not believed. Rav Ashi - agrees with his ruling regarding 'Amanah hayu Devareinu', but not regarding 'Moda'a hayu Devareinu', where he holds that he is believed.

We already cited Mar bar Rav Ashi (or Rav Ashi)'s reason by 'Amanah hayu Devareinu'. His source is the Pasuk in Iyov "Al Tashken be'Ohalecha Avlah".

We know that he disagrees with Rav Nachman's reasoning in this case (that the witnesses cannot negate a Sh'tar), even though he agrees with his ruling - because otherwise, he would not believe the witnesses by 'Moda'a hayu Devareinu either.

In a nutshell, he defines the difference between the two rulings inasmuch as - whereas 'Moda'a hayu Devareinu' is meant to be written ('Zeh Nitan Likasev'), 'Amanah hayu Devareinu' is not ('ve'Zeh Lo Nitan Likasev').

With regard to Mar bar Rav Ashi's ruling validating 'Moda'a hayu Devareinu' (even if they testify orally), he says 'Zeh Nitan Likasev' on the grounds that it is a Mitzvah to save a fellow-Jew from an Oneis that causes him a financial loss.

The witnesses are believed - even if their signatures are substantiated from another source.

Nor is it considered 'Chozer u'Magid - since 'Moda'a hayu Devareinu', which does not actually invalidate the Sh'tar, is considered an independent testimony (which only prevents him from claiming with it until the loan takes place).

It would be considered 'Chozer u'Magid' however - if they would claim 'Pesulim hayinu' or 'Anusim hayinu' (since this would render the Sh'tar invalid).

We learned in our Mishnah 'Ein le'Ish Chazakah be'Nechsei Ishto', and we ask why it is not obvious that, seeing as he is permitted to eat the Peiros of his wife's Nechsei Milug. The difference between this case and Mashkanta de'Sura, where the debtor needs to make a Mecha'ah (despite the fact that there too, the creditor permitted to eat the Peiros) is that - whereas here, everyone knows about the Takanas Chachamim permitting a man to eat the Peiros of his wife's Nechsei Milug, there, we are afraid that seeing as a few years have elapsed, people will forget that the creditor received the field as a Mashkon.

To answer the Kashya why it is not obvious, we establish our Mishnah - where the husband declared 'Din u'Devarim Ein li bi'Nechasayich' (effectively withdrawing his rights on the Peiros of Nechsei Milug).

Nevertheless, we initially suggest that he cannot establish a Chazakah on his wife's property - because his wife will be unlikely to protest even if he eats the fruit unlawfully, due to the fact that he sustains her.

The Beraisa rules that if someone says to his friend 'Din u'Devarim Ein li al Sadeh Zeh' (or a similar Lashon of withdrawal), intending to give him the field as a gift - the field remains his, because one cannot withdraw from something that one already owns (unless one specifically declares it Hefker).

To relinquish his rights on his wife's Nechsei Milug in this way - our Mishnah must be speaking where he did so during the engagement period (since all marital rights only come into effect after the Chupah).

de'bei Rebbi Yanai (the author of this answer), bases it on a statement of Rav Kahana regarding a 'Nachalah ha'Ba'ah lo le'Adam mi'Makom Acher' (i.e. an inheritance that a person receives by means of a Takanas Chachamim), regarding which ...

... Rav Kahana ruled that - he is able to withdraw in advance of receiving it ('Adam Masneh alehah she'Lo Yirshenah').

Rav Kahana's statement is based on a broader principle presented by Rava, who says that - one accepts the claim of anybody who declares that he rejects a gift that comes to him via a Takanas Chachamim ('Kol ha'Omer I Efshi be'Takanas Chachamim, Shom'in lo').

Rava in turn, said it in connection with a ruling of Rav Huna Amar Rav, who stated that - a woman who does not want to work for her husband, has the right to declare that she prefers not to be sustained by him and not to work for him ('Eini Nizones ve'Eini Osah').

Rava presented his principle specifically on Rav Huna Amar Rav's ruling -because that is what they happened to be learning in the Beis-Hamedrash at the time.

And the reason for the principle is - because the Chachamim did not want to impose their favors against the recipient's wishes.

A woman can ...

... decline to work for her husband (despite the fact that he is the one who will be losing out and not her) - because the initial Takanah was for her sake (that her husband should sustain her), and it was only to offset the ensuing breakdown of Shalom Bayis that Chazal added that her husband may take her work in exchange.

... retract, even after they are married, even though the Takanah has already taken effect - because practically, it only takes effect each day as she needs to eat.

In return for the right to eat Peiros of his wife's Nechsei Milug - a man is obligated to redeem her in the event that she is captured.

Should he not want the onus of redeeming her - he is permitted to relinquish his claim on the Peiros of his wife's Nechsei Milug ...

... because in this case, the Takanah was initiated for his benefit.

We can extrapolate from our Mishnah 'Ein le'Ish Chazakah be'Nechsei Ishto' that - although one cannot establish a Chazakah on one's wife's property, it is possible to obtain it through witnesses or a Sh'tar that his wife sold it to him.

The Mishnah in Gitin rules that if Reuven purchased all Shimon's fields (which are automatically Meshubad to his wife's Kesuvah) and then paid his wife a token fee for her rights in the fields, 'Mikcho Bateil'- meaning that the wife's sale is Bateil, and that, should the seller die or divorce her, her rights to claim her Kesuvah from any of those fields remain intact.

The reason for this ruling is - because she can claim that she only added her signature to the sale in order to make her husband happy, but that she did not really mean it.

We reconcile this with the previous inference from our Mishnah, by citing Rabah bar Rav Huna. To tally with our Mishnah, Rabah bar - Rav Huna establishes the Mishnah in Gitin by three specific fields, on which the woman particularly relies.

Two of those fields are fields 'she'Kasav lah bi'Kesuvasah' - a field which the husband designated in the Sh'tar, and 'she'Yiched lah bi'Kesuvasah' - one which he designated only orally (a regular Apotiki).

The third field upon which a woman implicitly relies is - one of her father's fields which she brought into the marriage, and which was assessed and inserted in the Kesuvah and on which her husband accepted responsibility (i.e. Nechsei Tzon Barzel).