Why does the Torah insert the (otherwise superfluous) word "Vehayah ha'Sadeh be'Tzeiso ba'Yovel"?
Erchin, 14b: On the one hand to incorporate a rocky field - which is called 'Sadeh' even though it is not fit for planting - in the current ruling, and on the other, to preclude trees - which do not fall under the heading of 'Sadeh' - and which do not therefore go to the Kohanim in the Yovel. 1
Refer to 27:16:1:41 and note.
Having stated "Kodeh la'Hashem", why does the Torah then add "ki'Sedei ha'Cherem..."?
Rashi: To teach us that the field does not go to Bedek ha'Bayis, 1 but to the Kohanim of the Mishmar that is serving in the Beis-Hamikdash when the Yovel begins. 2
Erchin, 29a: To teach us that the Din of Sadeh ha'Cherem - in Eretz Yisrael 3 - only applies when the Yovel applies.
Erchin, 34a: To learn the Sadeh Cherem that a Kohen declares from Sadesh Achuzah, which goes to the Kohanim who are serving in that Mishmar when the Yovel arrives - and that he cannot claim that, since he receives a portion in the Sadeh Achuzah of others, how much more so his own even though he is not serving in that Mishmar. 4
Why does the Torah refer to the field as "Kodesh la'Hashem"?
Erchin, 25a: To teach us that, when the Yovel arrives the Kohanim of that Mishmar may enter the field, but that, like Hekdesh, they must first redeem it. 1
See Torah Temimah, note 125.
How will we reconcile the current Pasuk " ... la'Kohen Tih'yeh" with Pasuk 28 "Kol Cherem ... la'Hashem"?
Erchin, 28b: S'tam Charamim go the Kohanim, whereas Pasuk 28 is speaking where the owner specifically declared 'Cherem la'Hashem'.
To which Kohen does the owner give the Cherem?
Erchin, 28a: Based on a Gezeirah Shavah "la'Kohen" "la'Kohen" - in Naso, Bamidbaar, 5:10 in connection with Gezel ha'Ger, 1 it goes to the Kohanim of the Mishmar that is serving when Yovel arrives.
See Torah Temimah, note 131.
Why does the Torah add the (otherwise superfluous) word "la'Kohen Tih'yeh Achuzaso"?
Erchin, 25b: To extrapolate "Achuzaso she'lo, ve'Ein Zu she'lo' - to teach us that, in a case where a Kohen redeemed a Sadeh Cherem of a Yisrael from the Gizbar and the Yovel arrives, it goes to the Kohanim of that Mishmar, and he cannot claim the field due a Kal va'Chomer - Refer to 27:21:1:3.
The Sifra extrapolates from "ha'Sadeh be'Tzeiso" that 'Sadeh' is masculine. What is the significance of that?
Da'as Zekenim and Moshav Zekenim: With reference to the Gemara in Bava Kama, 109b - that if a Kohen redeemed it, he cannot say 'If I can acquire what did not belong to me (if one does not redeem his field before Yovel, it is divided among the Kohanim), how much more so, am I permitted I keep what I redeemed!', because "ki'Sedei ha'Cherem Tihy'eh Achuzaso" refutes this. 1 Now if 'Sadeh' was feminine, we would say that the field is his inheritance! But since it is masculine; the field is Kodesh to Hashem, just like a Cherem field is to a Kohen.
Moshav Zekenim: An old text reads "Vehayah ha'Sadeh" teaches that it goes to the Gizbar, like it was before he sold it. If not, I would say that it is the Kohen's and he keeps it.
QUESTIONS ON RASHI
Rashi writes that "ki'Sedei ha'Cherem" teaches us that the field does not go to Bedek ha'Bayis, but to the Kohanim. Why will "La'Kohen Tih'yeh Achuzaso" not suffice?
Rashi is not learning the basic Din from "ki'Sedei ha'Cherem". What he means is that, if you will ask why the field does not go out to Bedek ha'Bayis, it is because it is compared to S'dei ha'Cherem, which go to the Kohanim.