Gemara

(Rav): If Reuven was Mekadesh Leah 'from now and after 30 days', and Moshe was Mekadesh her during the 30 days, she is forever Safek Mekudeshes.

(Shmuel): The Safek is for 30 days. Then, she is totally Mekudeshes to Reuven.

Rav is unsure whether 'after 30 days' is a Tanai (stipulation, that he not retract within 30 days), or a retraction (of 'from now'). Shmuel is sure that it is a Tanai.

(Beraisa): (If one said 'you are divorced with this Get) from now and after my death', she is Safek divorced and not divorced;

Rebbi says, such a Get is valid.

Kesuvos 82a (Rav Dimi citing R. Yochanan): If Reuven told Shimon 'be Moshech this cow (take it to your premises), but it is not yours until 30 days from now', 30 days later he acquires it, even if it is in a swamp.

Contradiction (Ravin citing R. Yochanan): The cow is not acquired 30 days later.

Resolution: It is acquired only if he said 'acquire from now.'

86b - Question (Rami bar Chama): If her husband gave her Get and said 'you are not divorced until 30 days from now' and she left the Get in Tzidei (the side of a) Reshus ha'Rabim (and it was still there at the end of 30 days), what is the law?

Version #1 - Answer #1 (Rav Chisda): Rav and Shmuel taught that seizure of orphans' property helps only if the property is in a Reshus ha'Rabim. This shows that she is not divorced (for a Get must be put "b'Yadah", into her hand or Reshus). Tzidei Reshus ha'Rabim is like a Reshus ha'Rabim.

Answer #2: We learn from Rav Nachman that she is divorced! He taught that if one said 'be Moshech this cow, but it is not yours until 30 days', he acquires it then, even if it is in a swamp. (A swamp is like Tzidei Reshus ha'Rabim.)

Rejection: No, a swamp is unlike Tzidei Reshus ha'Rabim.

Version #2 - Answer #1 (Rav Chisda): We learn from Rav Nachman that she is divorced. (A swamp is like Tzidei Reshus ha'Rabim.)

Answer #2: Just the contrary! We learn from Rav and Shmuel that she is not divorced (for Tzidei Reshus ha'Rabim is like a Reshus ha'Rabim).

Rejection: No, Tzidei Reshus ha'Rabim is unlike a Reshus ha'Rabim.

Rishonim

Rambam (Hilchos Gerushin 9:2): If a man said 'here is your Get. You are divorced only 30 days from now', she is not divorced until 30 days. If her husband died, or the Get was lost or burned within 30 days, she is not divorced.

Rambam (3): If she left it in Tzidei Reshus ha'Rabim and it was stolen or lost after 30 days she is divorced, since the Get was intact on the day of divorce and she designated it in a place that is not Reshus ha'Rabim.

Question (Ramach): Why does the Rambam say that she is divorced? R. Yochanan requires saying 'from now'! The Rif did not bring R. Yochanan or Rav Nachman. He holds that in this case she is not divorced. Perhaps 'from now and after 30 days' is a retraction. All the more so, 'you are not divorced until 30 days' is a retraction and requires another Meshichah (i.e. Nesinah).

Rashba (cited in Ran Kesuvos 46a DH ul'Inyan): Rami bar Chama and Rav Chisda hold that Rav Nachman discussed without saying 'from now', but we do not hold like them. If he did not say 'from now', he did not acquire (82a). To establish Rav Nachman like the Halachah, we must say that he said 'from now'. If a Get was left in Tzidei Reshus ha'Rabim or Reshus ha'Rabim itself, she is Safek divorced . If it is a Tanai, she is divorced no matter where it is. If it is a retraction, she is not divorced, for she cannot acquire through Chatzer in Tzidei Reshus ha'Rabim, a swamp or a Simta.

Rebuttal (Ran): We said that without 'from now', he does not acquire, i.e. according to R. Yochanan. It was not the Gemara's conclusion. We hold like Rami bar Chama and Rav Chisda. Even without 'from now', the sale and Get are valid. Why the Rambam rule that the sale is valid, but not the Get?

Magid Mishneh: The Rambam rules like Version #2. In Hilchos Mechirah he equates a Get without 'from now' to Meshichah 'from now'. He explained this way, for we are unsure about 'from now and after 30 days.' If it is a Tanai, the Get is valid even if it was torn. If it is a retraction, 'from now' does not help. The Ramban and Rashba also hold that we asked about 'from now.' The Rambam holds that Rav Nachman discusses 'from now', like we conclude on 82a. Or, Rav Nachman discusses even without 'from now.' We disagree then, for the Meshichah ceases before 30 days. The writing on a Get divorces. The writing is intact on day 30; it suffices for the Get to be in a place where a Kinyan can be made. The Rashba equates Meshichah and a Get. Without 'from now', if it was left in Tzidei Reshus ha'Rabim, she is not divorced.

Kesef Mishneh: The Magid Mishneh said that the writing on a Get divorces. After 30 days, his Nesinah (giving) ceased! This should disqualify divorce, just like a sale is invalid if the Meshichah ceased! Regarding a Get, even without 'from now', if he put it in her Reshus until after 30 days, she is divorced through her initial reception. Since it never left her Reshus, it is not like Tli Gitech (take your Get by yourself), for he gave it to divorce. We ask about without saying 'from now', but still we can learn from Rav Nachman (who discusses 'from now'), that a swamp and Tzidei Reshus ha'Rabim are unlike Reshus ha'Rabim. If they were like Reshus ha'Rabim, even saying 'from now' would not help, for the Meshichah ceased.

Ran (Kesuvos 45b DH Garsinan): The Ra'avad says that the question of a Get left in Tzidei Reshus ha'Rabim and Rav Nachman's law are when he said 'from now and after 30 days.' The Ra'avad says so because he holds that without 'from now', even if she finds the Get there and picks it up, it is Pasul due to Tli Gitech. Also, if Rav Nachman discussed' without 'from now', the cow would not be acquired, like we learned above (82a).

Rebuttal #1 (Sefer ha'Zechus 44b): If the Get were 'from now and after 30 days', we could not say that she is not divorced. This is Safek Gerushin!

Rebuttal #2 (Ran): We hold (Kidushin 59b) that 'from now and after 30' is a Safek. 'After 30' is a Tanai (if I will not retract within 30 days), or a retraction (from 'from now'). If our Sugya held that it is a Tanai, it would not matter where the Get or cow was later! Rather, it is a retraction, as if he never said 'from now'. This shows that we ask about one who said only 'after 30' (unlike the Ra'avad). The Get is valid if it never left her Reshus; we ask whether Tzidei Reshus ha'Rabim is like Reshus ha'Rabim. It is not like Tli Gitech, because he put it there for Gerushin, just he wants it to work only later. We learn from Rav Nachman, who validates a sale for after 30 days even without saying 'from now'. This shows that in the swamp is like in his Reshus.

Rosh (Gitin 8:7): We asked about a Get given to divorce '30 days from now', and she left the Get in Tzidei Reshus ha'Rabim. If she took it back at the end of 30 days she is divorced, even though she caused the Nesinah. There was a proper Nesinah at the beginning. Therefore, even though it ceased in between, if it is in her hand at the end, she is divorced due to the initial Nesinah.

Ba'al ha'Ma'or (Gitin 35b): Some say that if one said 'you are not divorced until after 30 days', even if he said 'from now' it does not help, for he specified that she is not divorced until after 30 days.'

Poskim

Shulchan Aruch (EH 146:1): If one divorced to take effect after a fixed time, she is divorced at that time comes, like a Tanai. However, he did not divorce until then, unlike divorced on Tanai. Therefore, divorce on Tanai requires a double Tanai and all other laws of Tana'im, but this does not. If he gave a Get to divorce 30 days from now', and he died, or the Get was lost within 30 days, she is not divorced.

Shulchan Aruch (2): If she left it in Tzidei Reshus ha'Rabim and it was stolen or lost after 30 days, she is divorced, since the Get was intact on the day of divorce and she designated it in a place that is not Reshus ha'Rabim. Divorce on Tanai takes effect when it is fulfilled if the Get is intact, even if it is not in her Reshus.

Beis Shmuel (2): This discusses a Tanai of 'if'. If he said Al Menas, the Get need not be intact. We must explain why the Get need not be in her Reshus.

Yad ha'Melech (Hilchos Ishus 7:10 DH v'Lulei): Divorce to take effect later is invalid, for the Torah requires Nesinah when the Get takes effect, unless he intended for the Get to take effect retroactively through a Tanai.