Gemara

13b (Mishnah): (Damages apply to) specific property.

(Ravina): This excludes if Reuven's ox damaged, and Reuven made it Hekdesh or Hefker. He is exempt.

Support (Beraisa - R. Yehudah): Even if the owner made his animal Hekdesh or Hefker after it damaged, he is exempt. "The owner was warned, and it killed" - the killing and bringing to trial must like one.

Also the final verdict must be like one, for it says "the ox will be stoned."

33a (Beraisa - R. Yishmael): The ox is evaluated in Beis Din.

R. Akiva says, the victim takes the ox (it was his from when it damaged).

R. Yishmael holds that the victim is like a creditor. The damager owes him money. R. Akiva holds that they are partners in the ox that damaged.

33b (Rav Nachman): According to R. Yishmael, if the damager sold the ox, the sale is invalid (since the victim has a lien on the ox).

Question (Beraisa): The sale is valid.

Answer: The sale is valid regarding working with it until the victim takes it.

(Rav Tachlifa bar Ma'arava - Beraisa) If he sold the ox, it is not sold. If he made it Hekdesh, it is Hekdesh.

The damager sold it. The Beraisa is like both Tana'im. If he sold it, it is not (permanently) sold, even according to R. Yishmael, for the victim has a lien on it (and can collect it). If he made it Hekdesh, it is Hekdesh. This is even according to R. Akiva, due to R. Avahu's law;

(R. Avahu): (Hekdesh of property with a lien against it does not really take effect.) We decree that the creditor pay something to Hekdesh when he collects it, lest people say that Hekdesh becomes Chulin without redemption.

(Beraisa): If a Tam damaged, before Beis Din judges the case, if it was sold or made Hekdesh, this stands.

A sale takes effect for work. Hekdesh takes effect for R. Avahu's law.

44b (Mishnah): We kill the ox of a convert who died without heirs (if it killed);

R. Yehudah says, we do not kill it, for it has no owner.

(Rav Huna): R. Yehudah exempts even if it had an owner, and he made it Hefker or Hekdesh after it gored.

90b (Beraisa): If an ox killed and damaged, we judge a Tam to stone it, but not to pay the damage. If it was Mu'ad, first we judge it to pay, then we judge it to stone it. If first it was judged for stoning, we do not then judge it to pay.

Question: Even if it was judged for stoning, we should judge it to pay!

Rishonim

The Rif and Rosh (1:16) bring the Gemara on 13b.

Rosh: Even though Chachamim argue with R. Yehudah, Ravina established the Mishnah like an individual, because Chachamim argue only about an ox that killed a person. All agree about an ox that killed an ox.

Question (R. Akiva Eiger 44b): Rashi holds that R. Yehudah requires that it have one owner until the final verdict. A victim collects even if it was sold or made Hekdesh (33b). This must be like Chachamim. The Rosh holds that Chachamim agree about an ox that killed an ox. We exempt only for Hekdesh or Hefker, for then no one owns the ox, but not if it was sold. How can he explain why the victim collects if it was made Hekdesh?

Answer #1 (Chasam Sofer CM 165): Also the Rambam says that Hekdesh exempts, and also (Halachah 7) that Hekdesh does not take effect! It seems that Kedushas ha'Guf (intrinsic Kedushah) takes effect, but Kedushas Damim (monetary Kedushah) does not, for it is as if it still has an owner, i.e. the overseer of Hekdesh, so the victim can still collect. The Rashba (33b DH Ha) says that R. Avahu discusses Kedushas Damim, but Kedushas ha'Guf uproots the lien and it is truly Hekdesh. If he held like the Rosh, even without this Hekdesh ha'Guf exempts, for now there is no owner! Also, if only Kedushas ha'Guf exempts, why must we say that Hekdesh exempts for there is no owner? In any case it uproots liens! Perhaps the Gemara had to say 'for there is no owner...' to exempt from killing the ox. However, the Rambam says that this is why he is exempt from paying! It seems that this is for when it became blemished afterwards and became Kedushas Damim. The lien would return, if not that it became permanently exempt when it had no owner.

Hagahah: The Me'iri (44b DH Shor) holds that even before the final verdict, an ox that killed a person cannot become Kedushas ha'Guf.

Answer #2 (Kehilas Yakov 14:8 DH uv'Sof): An addition at the end of Teshuvas R. Akiva Eiger 196 (Warsaw edition) says that while it is Hefker, all agree that the victim collects from it. The exemption is only after someone else acquired it. While it is Hekdesh, it is like Hefker.

Answer #3 (Chazon Ish 3:16): Hekdesh of a Tam doesn't truly take effect, for the victim's lien allows him to collect. Perhaps partial Hekdesh even of a Mu'ad does not exempt, for if it would damage now he would be liable.

Rambam (Hilchos Nizkei Mamon 8:4): If Reuven's ox gored, and Reuven was Makdish or Mafkir it, he is exempt. One is liable only if it had an owner at the time of killing and bringing it to trial.

Rambam (6): If a Tam damaged, and the owner sold it before the trial, even though it is sold, the victim collects.

Ra'avad, in Shitah Mekubetzes 13b: If he was Mafkir or Makdish it before the trial, he is exempt. We learn from "they will sell the ox and divide its money", that it has an owner at the time of payment.

R. Yehonason, in Shitah Mekubetzes 13b: Even though all agree that if the owner sold it it is not sold, Hefker is different. The buyer caused his own loss by paying for it. It still belongs to the original owner, as if he did not sell it. Hefker removes the owner's ownership from it, so there is no owner at the time of the trial.

Poskim

Shulchan Aruch (CM 406:3): If Reuven's ox gored, and he was Mafkir it, and Shimon acquired it, he is exempt. However, if Reuven was Mafkir it and acquired it back from Hefker, he is liable.

Prishah (2): It suffices that it had an owner at the time it killed and at the time of the final verdict.

Question (Be'er ha'Golah 5): The Gemara discussed a Mu'ad, like Rashi and Tosfos say. If it was Tam, the victim collects from the buyer. If so, he should also collect from the one who acquired it from Hefker!

Answer (Gra 1): The Gemara said the killing... (bringing to trial and final verdict must be like one). It did not say that the killing and final verdict must be like one, but in between it need not belong to one owner. We infer that we require (one owner) also at the trial. This is unlike Rashi (who exempts if it was sold before the final verdict).

Amudei Esh (107, brought in Sedei Eliyahu): The Gra derives that the Gemara does not require that it never changed ownership. If so, the Gemara would have said 'the killing and final verdict must be like one', which would include everything in between! Rather, we require only that it have the same owner at these two times. Therefore, if he himself acquired from Hefker, he is liable. However, if he sold it, it is as if there is the same owner at the end, for the buyer owns it due to the first owner.

Question (R. Akiva Eiger): The Gemara (90b) suggested that after an ox was judged for stoning, it should be judged to pay damage. Once it was sentenced, it is Hefker, so in any case it cannot be judged for damages!

Answer (Chasam Sofer): R. Yehudah learns damages from death only regarding a Tam, which pays from its body. We cannot learn to a Mu'ad, for which the owner is obligated to pay. Why did Be'er ha'Golah explain oppositely? Perhaps sentencing is not a change of ownership. We find that if someone else killed it, he must pay the owner (91b)! However, if so Kedushas ha'Guf would not exempt due to a new owner, for he is still the owner to get atonement through it! Also Kedushas Damim would not exempt, for he is still the owner to add a Chomesh if he redeems it!

Shulchan Aruch (4): If one sold or bequeathed it after it gored, he is liable.

Gra (2): The Rashba derived that it need not have the same owner, for if so the Gemara should have exempted if one sold or bequeathed it.