MISHNA: A woman is acquired by, i.e., becomes betrothed to, a man to be his wife in three ways, and she acquires herself, i.e., she terminates her marriage, in two ways. The mishna elaborates: She is acquired through money, through a document, or through intercourse.
From where do we derive that betrothal is accomplished through an item of monetary value? It is derived by means of a verbal analogy between the term expressing taking stated with regard to betrothal and from the term expressing taking with regard to the field of Ephron. How so? It is written here, with regard to marriage: “When a man takes a woman” (Deuteronomy 24:1), and it is written there, concerning Abraham’s purchase of the field of the Cave of Machpelah from Ephron the Hittite: “I will give money for the field; take it from me” (Genesis 23:13).
The Gemara explains: The number in the first clause serves to exclude a wedding canopy, which does not effect betrothal. The Gemara asks: And according to the opinion of Rav Huna, who said: A wedding canopy acquires a woman, and it alone could be a mode of betrothal, as derived by an a fortiori inference (see 5a), this number serves to exclude what?
The number (in the first clause) serves to exclude acquisition through symbolic exchange. Although a woman can be betrothed by means of money or an item of monetary value, she is not betrothed if she is given an item by symbolic exchange. The Gemara explains why this needs to be excluded: It might enter your mind to say that since the Sages derive the acquisition of a woman by verbal analogy between the term expressing taking stated with regard to betrothal from the term expressing taking with regard to the field of Ephron, it can be suggested that just as a field can be acquired through symbolic exchange, so too, a woman can be acquired through symbolic exchange. Therefore, the tanna teaches us that this is not the case.
The Gemara asks: And perhaps one should say that so too, it is possible to betroth a woman by means of symbolic exchange. The Gemara answers: This cannot be the case, as symbolic exchange is effective using an item worth less than the value of one peruta, and with an item worth less than the value of one peruta, a woman
does not render herself acquired by a man.