(Rava citing Rav Nachman): Macha'ah must be made in front of two people. He need not tell them to write (a document, they can write it on their own, since this benefits him, it gives him proof that he protested);

Moda'ah (one who is being forced to sell or give his property informs witnesses beforehand that he acts unwillingly, and intends to reclaim his property when the Ones no longer applies) must be made in front of two people. He need not tell them to write it;

Admission (I, Reuven, owe Ploni) must be made in front of two people. He must tell them to write it (for this hurts Reuven. Ploni could use the document to 'prove' that he was never paid);

Kinyan (Chalipin) can be done in front of two (Tosfos - or even without any onlookers). The giver need not tell them to write it;

Validation of documents must be in front of three judges.

Question (Rava): How do we understand Chalipin?

If (he need not tell them to write because) it is considered an act of Beis Din (Beis Din has the power to enact, even if it hurts a party), it should require three (like all acts of Beis Din)!

If it is not considered an act of Beis Din, he should have to tell them to write it (for this hurts the giver)!

Answer (Rava): Really, it is not considered an act of Beis Din. He need not tell them to write it, since he used Chalipin in order that the receiver will acquire immediately, so we assume that he wants the document to be written.

(Rabah and Rav Yosef): We write a Moda'ah only against one who does not obey Beis Din (otherwise, he should ask Beis Din to prevent the Ones).

(Abaye and Rava): Moda'ah may be written against people such as ourselves (who obey Beis Din. Sometimes, Beis Din is not available to prevent the Ones).

(Chachamim of Neharde'a): If the witnesses on a Moda'ah did not write 'we know the Ones', it is invalid.

Question: What is the Moda'ah about?

If it is a Moda'ah to invalidate a Get or gift, surely he is Anus! (Since the giver does not receive anything, Ones is the only reason he would give the document if he does not want it to take effect.)

Suggestion: It is about a sale.

Rejection: Rava taught that we do not write a Moda'ah about a sale!

Answer: Really, It is about a sale. Rava admits when there is an Ones, like the following case.

Reuven's orchard was a Mashkanta to Shimon for three years. After three years, Shimon threatened 'if you do not sell it to me, I will conceal the Mashkanta document and claim that I bought it.' (He would be believed, because he had a Chazakah, i.e. Reuven never protested.)

(Rav Yehudah): One cannot collect with a concealed gift document. (Perhaps it was only intended to be a Moda'ah (to invalidate a second document that will be written for the same property), or the property was already given to someone else).

Question: What is a concealed gift document?

Version #1 - Answer (Rav Yosef): The giver told the witnesses 'seclude yourselves and write it.'

Version #2 - Answer (Rav Yosef): He did not tell the witnesses 'write it in the market, in public view.'

Question: What is the difference between these answers?

Answer: They argue about one who gave no instructions where to write it.

(Rava): It does work like a Moda'ah.

(Rav Papa): Rava did not say this explicitly. Rather, it was inferred from the following.

Reuven wanted to be Mekadesh Leah. She agreed to accept only if he will write all his property to her; he agreed. Reuven's oldest son complained to him (before the document was written) 'what will I inherit?!' Reuven commanded witnesses to hide themselves and write his property to his son.

(Rava): Neither the son nor Leah acquires the property.

Someone heard this ruling, and assumed that it is because a concealed gift works like a Moda'ah.

Rejection: No, Rava ruled like this only in this case, for it is evident that Reuven did not want to give to Leah;

In a case where the unconcealed gift was given willingly, this shows that the giver wants it to be valid. The concealed gift is not a Moda'ah!

Question: What is the law when he gave no instructions where to write it? (I.e. which version does the Halachah follow?)

Answer #1 (Ravina): The document is valid.

Answer #2 (Rav Ashi): It is invalid.

The Halachah is, it is invalid.