Gemara

157a (Mishnah): A house fell on Reuven and his father or Morishav (someone else whom Reuven inherits). Reuven left creditors. The creditors say that the father died first (and Reuven inherited him, so they may collect from the father's property). His father's heirs say that Reuven died first.

159a: If Reuven sold his father's property in Yakov's lifetime, and Reuven died, and Yakov died, Reuven's son (Chanoch) takes from the buyers. A Beraisa calls this law difficult, for the buyers should be able to say 'you do not inherit what your father sold!'

Objection: This is not difficult! Chanoch can say 'I do not take because I inherit Reuven. Rather, I inherit Yakov - "Tachas Avosecha Yihyu Vanecha."'

Answer: "Tachas Avosecha Yihyu Vanecha" is merely a blessing (that a Tzadik will have children to inherit him).

Question: It is not merely a blessing. The law is true!

(Mishnah): A house fell on Reuven and his father or Morishav. Reuven's creditors say that the father died first...

Suggestion: The father's heirs are Reuven's sons. 'Morishav' is Reuven's brother. If a grandchild does not directly inherit his grandfather, the verse is merely a blessing. Even if Reuven died first, the creditors should collect, for the property passes to Reuven before it goes to Reuven's sons!

Answer: No, the father's heirs are Reuven's brothers. 'Morishav' is Reuven's uncle.

Bechoros 51b (Mishnah): A woman collects her Kesuvah from Muchzak, but not from Shevach (improvements made to the property) or Ra'uy (property that came to her husband after he died).

A Bechor does not receive a double portion of Shevach, nor from Ra'uy for it says "b'Chol Asher Yimatzei Lo" (at the time of death.)

Question: Why does our Mishnah say that a woman does not collect Shevach? (She is like a creditor.) Shmuel taught that a creditor collects Shevach!

Answer (R. Aba): This is a weakness of rights to collect a Kesuvah.

Kesuvos 55a (R. Yanai): Stipulations of the Kesuvah are like the Kesuvah also regarding Shevach (they are not collected from it).

Rishonim

Rambam (Hilchos Nachalos 5:8): A house fell on Reuven and his father or another of Morishav. Reuven owed creditors. The father's heirs say that Reuven died first without property, so the creditors lost their debt. The creditors say that the father died first and Reuven inherited him, so they may collect from the father's property. The property is in the Chazakah of the heirs. The creditors must bring a proof, or they collect nothing.

Rosh (Bechoros 8:11): The Mishnah teaches that a woman does not collect her Kesuvah from Ra'uy. A Tosefta teaches that also damages are not collected from Ra'uy. This shows that the Mishnah does not teach a woman to exclude creditors; also creditors do not collect from Ra'uy. The Mishnah teaches only a woman, for she does not collect Shevach. This is unlike R. Efrayim, who says that this is like a leniency of Kesuvah, but creditors collect from Ra'uy. R. Chananel was unsure about this. A Mishnah (Bava Basra 157a) explicitly teaches this! The Gemara says that the father's heirs are Reuven's sons, who come to inherit their grandfather. This shows that a a creditor does not collect from Ra'uy, even if he wrote '(you will have a lien on) what I will acquire.' The Yerushalmi expounds from "Meitav Karmo", but not from Ra'uy. E.g. Shimon dug a pit and it damaged in his lifetime. After he died, property fell to him (and Shimon's son inherited it). The verse teaches that the victim has no lien on the property.

(Gra CM 104:36): Tosfos (159 DH v'Limru) says that there is no proof that a creditor does not collect from Ra'uy. The creditor does not collect because grandchildren inherit directly from their grandfather! However, the Yerushalmi requires the verse to teach that one does not collect from Ra'uy. The Ramban learns from Kesuvos 55a, which says that Tanai Kesuvah are like the Kesuvah regarding Shevach. It does not say regarding Ra'uy (for no creditor collects from Ra'uy).

Ramban (125b DH Od): A creditor does not collect from Ra'uy. The borrower was unable to sell it, so he cannot put a lien on it!

Hagahos Ashri (9:38): If property fell to Reuven after his death from his mother's father, his paternal brother can inherit only due to Reuven, therefore Reuven's creditor collects from the property.

Mordechai (574): Even though a Ba'al (some teextra share add the word 'Chov') and Bechor are weak regarding debts (owed to him or his father), and it is considered Ra'uy, a Kesuvah is collected from a debt. If a worker did not collect wages in his lifetime, all agree that it is Ra'uy, and a Kesuvah or food is not collected from it.

Poskim

Shulchan Aruch (CM 104:16): If David borrowed and had no money to pay, and a house fell on him and Morishav, and his children say 'our father died first, and inherited in the grave, the creditor may not take from the property' (Rema - because a creditor does not collect from Ra'uy), and the creditor says that Morishav died first and he may collect from the property, the Halachah follows the heirs.

SMA (36): The Mordechai (Bava Basra 574) says that a creditor does not collect from wages that a worker did not receive in his lifetime for this reason (a creditor does not collect from Ra'uy). The Darchei Moshe says so in the name of the Ramban. This is unlike the Beis Yosef (107:3) brings from Sefer ha'Terumos citing the Rosh (from Lun'il), that if he said 'you may collect from propery that I will acquire', the creditor collects from property that the borrower's children inherited from their father. The Maharshal (Teshuvah 49) says that a Shtar Chetzi Zachar (a document that says that a son-in-law will receive half as much as a son inherits) 'from Muchzak and Ra'uy' takes effect on what the father-in-law inherits after his death. The Rema said otherwise; the Maharshal disagreed. The Tur (107:16) writes that a creditor collects from a loan that came to the borrower after he died, even though it is considered Ra'uy regarding a Bechor.

Rebuttal (Shach 21): The Mordechai says that a Kesuvah is not collected from Ra'uy. The text says that a loan is Ra'uy to a Ba'al (not to a Ba'al Chov). The Maharshal was unsure whether a creditor collects from Ra'uy. The Shtar Chetzi Zachar does not work because a creditor collects from Ra'uy. Rather, one can stipulate about Ra'uy. If the heirs want, they can pay the entire debt (from what their father left when he died), and the son-in-law will not receive like stipulated.

Shach (21): Also the Tur says that a creditor does not collect from Ra'uy. This is not necessarily true. Rather, the creditor does not collect because the heirs say 'we inherit our grandfather', like Bava Basra 159 and Hagahos Ashri. If so, the creditor collects when the heir cannot say this. Hagahos Ashri says so. The Maharshal and Rema were unsure about this; in any case, the Halachah in this Sa'if is true because he can say that he inherits his grandfather. The Rosh (from Lun'il) says that his law is unlike the Rif, who says that David can take (his grandfather's property) from one who bought it (from David's father). I say that the Rif could agree that a creditor collects from Ra'uy, but in the above case David can say that he inherits his grandfather. The Rema says that even though the Rosh holds that a creditor collects from Ra'uy, he could agree to the Mishnah, for the grandson inherits his grandfather. This is wrong. The Rosh explicitly rules like a creditor does not collect from Ra'uy! The Ramban (Sefer ha'Zechus Kesuvos 40a, Milchamos Hash-m Bava Metzia 7b) says that R. Chananel holds like this. It seems to me that he collects! The Sugya 123-124 proves that Shevach is Ra'uy. In Bechoros, we learn about Shevach from the same verse that teaches about Ra'uy. We hold that a creditor collects Shevach. One could find flimsy reasons to distinguish between Ra'uy and Shevach, but why should we?! Sefer ha'Terumos says that the Ramban proved from the Tosefta and Yerushalmi that he does not collect Ra'uy. I say that they prove that he collects! A verse ("Karmo") was needed to teach that damages are not collected from Ra'uy. A Yavam does not get an extra share from Ra'uy, for he is equated to a Bechor. There is no verse for a creditor, so he collects from Ra'uy! Here, the Rema explains the Mechaber, who says that the borrower's children say that their father died first and inherited in the grave, and they inherit him, i.e. they do not directly inherit their grandfather. If so, the Mechaber must hold that a creditor does not collect from Ra'uy. The Rema himself was unsure. Sefer ha'Terumos cited the Rosh of Lun'il. Sefer ha'Terumos preceded the Rosh of Tultila (who wrote the Pesakim), who explicitly says that a creditor does not collect from Ra'uy.