My question is that tosfos on top of 2b asks that why does the gemara bring a passuk from nach that kesef is a kinyan it should have brought a passuk from the torah? So tosfos answers that the reason why we bring this passuk is because it wants to teach us about a kinyan of a field. Now first of all I'm not sure what that means. and 2nd of all why do we have to bring a passuk about a field as long as we find any passuk which uses the loshon of kinyan by kesef that should be enough of a reason why we use a Loshon kinyan in our Mishna so why does tosfos say we are bring a passuk of ??? but any passuk which uses by kesef a Loshon kinyan should also be fine?
Many thanks
Benzi
Benzi, London
1) It seems to me at the moment (I got this idea partly from the Atzmos Yosef, DH Gemara v'Kichah) that the Pshat is as follows. We learn in the Mishnah below (26a) that fields can be acquired through money, deed of sale, or Chazakah. However, we do not yet know the source from the Torah for all of those three ways. It is possible to think at the moment that there is no Kinyan mid'Oraisa of Kesef for a field. It could be that the only way to acquire a field is through a deed of sale, for instance. That is why Tosfos writes that the Gemara wants to teach us the Kinyan of a field, because otherwise we would not know for sure that the field bought by Avraham could be bought by money.
2) After thinking more about this question, I think what I wrote is correct but I found also a different explanation, in Otzar ha'Chochmah, in a Sefer by the name of Meir Derech on Kidushin. He says that the reason why Tosfos writes that the Gemara wants to cite a verse about Kinyan for a field is that Tosfos is consistent with what he writes above (2a, DH v'Kesef), that the Gemara had to cite a proof that the Kesef -- from which Kidushin with a woman is derived -- is called a Kinyan.
Since the Kesef from which Kidushin with a woman is derived is stated in connection with a field, it follows that the Gemara wanted to cite a verse connected with a field.
Kol Tuv,
Dovid Bloom
P.S. Just as an anecdotal note. I remember that once I went to the house of Dayan Kaplan zt'l, of the London Beis Din, to ask a question, and there was a copy of Sefer Atzmos Yosef on his table!
So really the gemara could have brought any passuk where we see that kinayn is used by kesef, but the reason why it brought down a passuk by a field was because the gemara beforehand brought down a passuk of a field. Is that correct?
I suppose that is correct, but we must add that it was not by accident that the Gemara before brought a verse about a field. "Kichah-Kichah" is a Gezeirah Shavah which is a Halachah l'Moshe mi'Sinai. This is the only way we have of deriving that Kidushin with a woman can be performed by Kesef. Since it is only through a verse about a field that we learn Kidushei Ishah, it follows that Tosfos (beginning of 2b) writes that we have to bring a verse about a Kinyan of a field.
Kol Tuv,
Dovid Bloom