פירוש על קידושין 3:4

The word “acquisition” is used because the law that betrothal can be effected with money is derived from the use of the word “taking” in two contexts—betrothal and the transfer of money when Abraham buys the field from Ephron. Since buying something is called an “acquisition” (two prooftexts are cited), taking a woman in betrothal is called, at least by this mishnah, “acquisition.”

"And where does [the use of] money [in betrothal] come from? We learn 'take' 'take' (קיחה) from the field of Efron." [Problem:] But if you say: What do I need all this for!? [the Talmud] only needed to say "Money is called acquisition (קניין), as it is written, 'I gave money of the field, take from me' and it is written 'The field that Avraham acquired'; or: 'Fields are acquired with money'"! Solution: It is because this wouldn't have been enough for, even granted that money for a field is called acquisition, money of a wife is not called acquisition. Therefore it needed to bring evidence of that money, for we learn from it that [money for] a wife is called acquisition.

"It's written there 'I gave money of the field, take from me'". [The Talmud] is only concerned about finding the terminology of "take" (קיחה), since it is not similar because the "take" here is about the money of a field, while "take" for a wife is not about money but rather about the wife herself. [Problem:] But if you say: Let it teach "The wife is purchased (נקחת)", for this is more the terminology of Scripture as it is written "When he purchases", and we teach also in Eruvin "Anything can be purchased with tithe money", and it is also fitting to use the terminology of קיחה for sex, as it is written "A man that purchases his sister" (Vayikra 20:17)!? Solution: It would not have been fitting to teach at the end "and she purchases/takes herself in 2 ways".