Gemara

(Rava): In the absence of the borrower (Reuven), we write an Adrachta to collect land, but not for Metaltelim. We are concerned lest Shimon (the lender) consume them, and later Reuven will bring witnesses discrediting the document, and Shimon will not have anything to return to him.

If Shimon has land, we may write an Adrachta on Reuven's Metaltelim. We are not concerned lest Shimon not have anything to return to him.

Rejection: Even if he has land, we do not write an Adrachta on Metaltelim, lest Shimon cause the land to decrease in value.

Pesachim 30b (Abaye): When a creditor collects (Meshubad property, i.e. he had a lien on it), this is retroactive (as if he collected from the time of the loan);

(Rava): He collects from now (not retroactively).

Kesuvos 93b (Mishnah): If a man married four women and he died, the widows receive their Kesuvos in order. The first woman must swear to the second (that she did not already receive her Kesuvah), the second to the third, and the third to the fourth. The fourth receives her Kesuvah without swearing;

Ben Nanas says, does she profit because she is last?! Rather, also she does not collect without swearing.

94a (Shmuel): The case is, (after three women collected they found out that) one of the husband's fields was not really his. The first Tana holds that collection out of order is invalid (so there is no harm if the fourth woman collects without an oath). Ben Nanas holds that it is valid collection.

(Rav Nachman): All invalidate collection out of order. They argue about whether or not we are concerned lest the fourth woman decrease the field's value.

(Abaye): (The case is, adult orphans want the fourth woman to swear.) They argue about Abaye Kashisha's law (that one must swear to orphans to collect from them, even if they are adults).

Ben Nanas holds like Abaye Kashisha. The first Tana does not.

Erchin 7b (Rav Ada bar Ahavah): If Reuven had five Shekalim, and he said "Erki Alai", and again said "Erki Alai", if he gave four Shekalim for the latter Erech and one for the former, he was Yotzei for both.

All his money is Meshubad to the first Erech. It is as if he had no money for the latter. B'Di'eved, the money he gave for the latter Erech is valid, just like a creditor who collected before earlier creditors of the same borrower.

Rishonim

Rif (Kesuvos 53a): We hold that collection out of order is invalid. In Erchin, we say that it is valid. Rav Shrirah Gaon says that this is only regarding Hekdesh, for Hekdesh does not take from Hekdesh. A commoner takes from a commoner. This refers to land. Collection of Metaltelim (out of order) is valid, for it has no Kol.

Rosh (Kesuvos 10:11): Rav Hai Gaon, R. Chananel and the Rif invalidate collection out of order, for the Halachah follows Rav Nachman in monetary laws. Also, according to Shmuel, Chachamim invalidate it. The Halachah follows Chachamim against an individual.

Rambam (Hilchos Malveh 20:1): If Reuven owed many people, the earliest debt collects first, from Reuven himself or from people who bought his land. If a later creditor collected first, we take the property from him. This refers to land that Reuven had when he borrowed. If he bought land after borrowing from many people, even though he wrote to all 'what I will acquire is Meshubad to you', there is no precedence. Whoever collected it, even the last creditor, keeps it.

Magid Mishneh: Some Ge'onim say that collection out of order is valid. The primary opinion holds that it is invalid. In any case if a later creditor collected Beinonis and left Ziburis with the borrower, the collection was valid.

Question (Tosfos Kesuvos 90a DH Shema): Why do we say that if a later creditor collected, he keeps it? He should be no better than a buyer. An (earlier) creditor can take from a buyer!

Answer #1 (Tosfos): Indeed, Chachamim made a later creditor better than a buyer. This is an enactment, lest people be dissuaded from lending. Even though the earlier creditor loses, people will not be dissuaded, for one can collect first. In Erchin, what he paid for the latter Erech is valid, just like a later creditor who collected, even though there is no reason to enact lest lenders be dissuaded. There, since both creditors are Hekdesh, we are not concerned. Alternatively, that refers to Metaltelim. If a later creditor collected land, he does not keep it.

Answer #2 (Ramban Kesuvos 90a): Each Erech is a Milveh Al Peh. Whoever cannot be Toref Meshubadim cannot be Toref from one who collected a debt.

Poskim

Shulchan Aruch (CM 104:1): If Reuven owed many people, the one whose document has the earliest Kinyan collects first, from land or Metaltelim. This is even if the loan with the later Kinyan was due to be paid before the earlier loan. This applies to collecting from Reuven or from people who bought his land. If a later creditor collected land first, even if it was in front of the earlier creditor (Levi) and Levi was quiet, we take the property from him.

Beis Yosef (DH Kosav ha'Rashba): The Rashba (929) says that nowadays people are Meshabed Metaltelim Agav land, so if a creditor collected and left Metaltelim (for earlier creditors to collect), he keeps it. Collection is invalid only when an earlier creditor will lose his debt, but not if he can collect, even from Ziburis. If he left a loan document with the borrower, it seems that we do not collect from it, for it has no intrinsic value, but great Poskim collect from it.

Beis Yosef (DH u'Mah she'Chosav Rabeinu Afilu): The Rashba (1111) and Sefer ha'Terumos say that the Halachah follows Rava, who says that a creditor collects from now and onwards. This refers to a lender who sold the borrower's properly before the collection date came. All agree that the lien is from when the Kinyan was made, or from when he received the document, even if no Kinyan was made. R. Yerucham says that a stipulation to a later creditor 'you may collect whenever you want' does not help.

Beis Yosef (DH u'Mah she'Chosav v'Im): If a later creditor collected and sold the property to one from whom it cannot be collected, e.g. a Nochri or someone unknown, he is liable to pay due to Garmi, for damaging property Meshubad to someone else.

Rema: If a later creditor comes to collect land, we help him collect. When an earlier creditor comes, he can take what the later creditor collected.

Taz: We are concerned lest a creditor ruin the land only when (the borrower is away and) perhaps he will show that the document was forged or paid.