Gemara

(Rav Nachman citing Rabah bar Avuha): If orphans collected land for a debt owed to their father, a creditor of their father can collect that land.

Bava Kama 33b (Rav Huna brei d'Rav Yehoshua): We learn from a Beraisa that if Reuven damages land Meshubad to Levi (he has a lien on it), he is exempt.

Question: Rabah already taught that one who burns Ploni's documents is exempt!

Answer: One might have thought that there he can say 'I burned only paper', but for a real action, such as digging pits on a field, he would be liable.

40b (Beraisa - R. Noson): "He will give to the one he sinned against" - if Reuven owes to Shimon, and Shimon owes to Levi, we take from Reuven to pay Levi.

Rishonim

Rif and Rosh (Kesuvos 6a and 2:9): If Reuven owes to Shimon, and Shimon owes to Levi, we take from Reuven to pay Levi.

Rambam (Hilchos Malveh 2:6): If Reuven owes 100 to Shimon, and Levi owes 100 to Reuven, we take from Levi and give to Shimon. Therefore, if Reuven had no property and he had a loan document against Levi, and Levi said that it was a document of Emanah (the loan was never given) or it was paid up and Reuven agreed, we ignore his admission. Perhaps they scheme to uproot Shimon's collection rights. Rather, Shimon swears and collects from Levi, like anyone who is Toref (collects from one who bought from the borrower), who collects only with an oath.

Hagahos Ashri (Bava Kama 4:4, citing Or Zaru'a): R. Noson's law applies to a debt due to a loan... or Moser (inciting the kingdom to take another's money). R. Simchah argues about a Moser.

Shach (CM 86:2): A Moser pays due to the law of Garmi. R. Simchah holds that this is only mid'Rabanan, therefore Shibud d'R. Noson does not apply to it. I say that even so, Chachamim enacted like Torah law. We do not find anyone who distinguishes between mid'Oraisa and mid'Rabanan debts regarding Shibud d'R. Noson.

Hagahos Ashri (ibid.): If a congregation imposed a tax, someone holding a deposit of someone liable to pay the tax must give it, due to Shibud d'R. Noson. If Reuven owed Shimon and Levi stole from Reuven, we take from Levi to pay Shimon. R. Chananel rules like R. Noson, provided that we know that he still owes him. If Reuven says that he paid Shimon, Avi ha'Ezri was unsure whether Levi can make him swear.

Beis Yosef (DH Kasuv bi'Teshuvas): I say that surely Levi cannot make him swear, for Levi is unsure! He can impose a Stam Cherem (against one who falsely claims that he paid).

Hagahos Ashri (ibid.): R. Meshulam says that if Reuven paid Levi before Beis Din obligated him due to Shibud d'R. Noson, he must pay also Shimon.

Teshuvos Maimoniyos (Mishpatim 9): This requires great investigation.

Hagahos Ashri (ibid.): Shibud d'R. Noson is only when Levi borrowed from Shimon before Shimon borrowed from Reuven. It is only when Reuven himself could have collected. A husband does not inherit money owed to his wife for damage or a loan, even though had she collected in her lifetime the money would have become Nichsei Melug.

Mordechai (31, citing Rabbeinu Meir): If Reuven dug in land Meshubad to Levi, since he must pay the owner, he should owe Levi due to R. Noson's law! My Rebbi derived that R. Noson's law applies only when Shimon (who owes and is owed) lent before he borrowed. Then, when he becomes Meshubad to Levi, also Reuven becomes Meshubad to Levi. It does not apply here, for Shimon owed Levi before Reuven owed Shimon. I reject this proof. Here, Shimon damaged his own property that was Meshubad to Levi!

Poskim

Shulchan Aruch (CM 86:1): If Shimon owes 100 to Reuven, and Levi owes 100 to Shimon, we take from Levi and give to Reuven. We do not distinguish whether or not Levi already owed Shimon when Shimon borrowed from Reuven.

Beis Yosef (DH u'Mah she'Chosav Rabeinu): This is like the Tur. Hagahos Ashri (Bava Kama 4:4) and the Mordechai (Bava Kama 31) apply Shibud d'R. Noson only when Shimon lent to Levi before Reuven lent to Shimon.

SMA (1): R. Noson expounds that "Asham" refers to the Keren (principal). When Reuven lent first, we can say that Shimon lent Reuven's Keren to Levi. Rather, even when Shimon lent first, it is called Reuven's Keren, for he will collect it after Shimon collects it from Levi. There is also a reason to say oppositely. When Shimon lent first, when Reuven later lent to Shimon, his lien takes effect on all Shimon's property and everything Meshubad to Shimon, i.e. Levi's property. Rather, even when Reuven lent first, and later Shimon lent, Reuven gets a Shibud against Levi. The latter reasoning is better. Sefer ha'Terumos holds like it.

Shulchan Aruch (3): Even when Shimon has no property, Reuven cannot force him to claim from Levi and pay. This toil is not incumbent on Shimon. Rather, Reuven must toil to collect from Levi.

Source #1 (Gra 13): If Reuven (Ploni's creditor) collected a field that Ploni sold, Ploni can take Reuven to Beis Din to contest this. Reuven cannot say 'you have no claim against me', only because Ploni needs to compensate the buyer (or similar concerns - Bava Kama 8b). This implies that Reuven himself takes from the buyer. Shibud d'R. Noson is like collecting from a buyer.

Source #2 (Beis Yosef DH v'Af): Sefer ha'Terumos derives this because it says 'we take.' I.e. Beis Din takes, not Shimon. Also, a borrower need not sell his property to pay money. The toil to claim from Levi is like the toil to sell.

Rebuttal (Shach 8): 'We take' refers to when Shimon is not here, or when Levi refuses to pay. When Shimon is here, he is not Yotzei until he pays, therefore he must utilize all possible ways to collect from Levi and pay Reuven. A borrower need not sell Metaltelim to repay money, for Shavah Kesef is like Kesef (but here, he did not pay). Perhaps Sefer ha'Terumos, the Tur and Shulchan Aruch discuss when Shimon gives appraised documents, which are like Shavah Kesef. Normally, documents are not Shavah Kesef. All the more so Shimon is not Yotzei by authorizing Reuven to collect from Levi! If Shimon does not claim from Levi in order to try to pay Reuven, we apply to him "a Rasha borrows and does not pay."

SMA (6): If Shimon wrote 'I accept to deal with the merchandise, sell it, and pay money', the toil (to collect from Levi) is included.

Beis Yosef (DH u'Motzasi): Rav Amram Gaon ruled that we do not take from Levi to pay Reuven until Reuven claims from Shimon. If Shimon does not pay, then we take from Levi, after Reuven swears that he was not paid. If Shimon died before Reuven claimed from him, Reuven must claim from Shimon's orphans before collecting from Levi. The Yerushalmi supports this.

Shulchan Aruch (107:1): It is a Mitzvah for orphans to pay their father's debt. We force them just like we would force their father. This is if they inherited land, but not if they inherited Metaltelim. However, the Ge'onim enacted that a creditor collects from Metaltelim that orphans inherited, so nowadays we force them even if they inherited Metaltelim. Similarly, they must pay from a loan owed to their father, whether they collected land or Metaltelim.

Beis Yosef (Kosav ha'Rashba): The Rashba explains that Rav Nachman taught that if orphans collected land for a debt owed to their father, a creditor of their father can collect that land due to R. Noson's law. If the orphans collected Metaltelim, a creditor of their father cannot collect it, for a creditor has no lien against Metaltelim of orphans.

SMA (4): According to the Gemara (before the Ge'onim's enactment), they must pay only if they collected land.

Shach (3): Due to R. Noson's law, Reuven can collect even Metaltelim of orphans of Shimon, who borrowed from Levi (who borrowed from Reuven).