Gemara

(Mishnah): If we find the murderer before Arifah (beheading a calf for atonement when a murdered corpse is found, it is permitted, and) it returns to the flock;

If we find him after Arifah, it is buried in its place;

This is because from the beginning, it was brought due to Safek. It atoned for the Safek.

25a (Rava): Eglah Arufah becomes forbidden after Arifah;

(Rav Hamnuna): It becomes forbidden when it is alive.

(Rabanan): Presumably, when it is taken to the Nachal Eisan it becomes forbidden.

Support (Rava, for himself - Mishnah): If we find the murderer before Arifah, it returns to the flock.

Answer: Tana'im argue about this;

(Beraisa): The Torah discusses Machshirim (things that permit) and atonements brought in the Mikdash, and Machshirim and atonements brought outside;

In the Mikdash, the laws of Machshirim (e.g. Asham Metzora, which allows him to eat Kodshim) and atonements (Chata'os and Ashamos) are the same (they must be Kosher Korbanos). Also outside the Mikdash, the laws of Machshirim (Tziporei Metzora, i.e. birds used for his Taharah) and atonements (Se'ir ha'Mishtale'ach, i.e. the goat sent to Azazel on Yom Kipur and Eglah Arufah) are the same. (Just like the goat, which is Kodshim, is surely forbidden while alive, also the birds, and all the more so we learn one atonement (Eglah) from the other.)

Sanhedrin 47b (Abaye): If one wove a garment for a Mes, one may not benefit from it;

(Rava): One may benefit from it.

Abaye forbids, because Hazmanah (designation) takes effect. Rava disagrees.

Abaye learns a Gezerah Shavah "Sham-Sham" from Eglah Arufah. Just like the calf is forbidden through designation, also designation for a Mes forbids.

Rava learns the Gezerah Shavah "Sham-Sham" from idolatry. Just like Hazmanah does not forbid (a Keli to serve) idolatry, also designation for a Mes.

He holds that it is better to learn Meshamshim (things used for a Mes) from Meshamshim (of idolatry), and not from Eglah Arufah, which is itself forbidden.

Berachos 26a (Mishnah): (To say Shma,) one must distance himself four Amos from urine and excrement.

(Rava): This suffices only if it is in back of him. If it is in front of him, he must distance himself as far as he can see.

The same applies to prayer.

Question: Rav Chisda permits praying while facing a Beis ha'Kisei!

Answer #1: That is when there is no excrement inside.

Objection: Rav Yosef taught that (the Isur to pray near) a Beis ha'Kisei is even if there is no excrement inside!

Answer #2: Rather, Rav Chisda permits praying facing a new Beis ha'Kisei. (It was not used yet.)

Question: Ravina never resolved whether or not Hazmanah for a Beis ha'Kisei takes effect (to make it like a Beis ha'Kisei)!

Answer: His was unsure whether one may pray inside it, but surely one may pray facing it.

(Rava): Even if there is excrement in a Persian latrine, it is considered sealed (so one may pray there).

Nedarim 7a - Question (Ravina): Do Yados work for (Hazmanah, i.e. designation of) a Beis ha'Kisei?

Question: If he said "this enclosure will be a Beis ha'Kisei, and this one, too", surely also the latter is a Beis ha'Kisei!

Answer: The case is, he said only "and this one" without saying "too." Does he mean that it also will be a Beis ha'Kisei, or that it will be it for other uses?

Question: Ravina's question assumes that designation for a Beis ha'Kisei takes effect. Elsewhere, Ravina asked whether designation for a Beis ha'Kisei or bathhouse takes effect!

Answer: He asked whether designation takes effect, and if you will say that it does, whether or not Yados work.

This is not resolved.

Rishonim

Rambam (Hilchos Kri'as Shma 3:3): If a new Beis ha'Kisei was prepared and not used yet, one may read Shma facing it, but not in it.

Ra'avad: The Rif said that the question was not settled. He did not write 'we are stringent' like he wrote about excrement stuck on one's shoe. We can say that here we are lenient, because we hold that Hazmanah is not significant. We asked about whether we decree, or if we are concerned for disgrace. Therefore, we are lenient about a Safek.

R. Yonah (Berachos 17b DH v'Davka): An old Beis ha'Kisei is forbidden even if now there is no excrement in it, due to "v'Hayah Machanecha Kodesh." Whatever the Torah forbids, also four Amos facing it is forbidden. A new Beis ha'Kisei is permitted even inside, and all the more so facing it. Persian latrines, even if there is excrement in them, are considered sealed. Chachamim of France say that even though our privies are like the Persians', since there is always urine there, we do not consider them to be sealed, and they are forbidden. Rav Hai Gaon says that theirs were on an incline, so the urine descends immediately, therefore they are considered sealed, and they are permitted. Ours are not on an incline, so they are forbidden.

R. Yonah (DH v'Hazmanah): The Rif did not say (about Hazmanah) 'we are stringent' like he wrote about excrement stuck on one's shoe. This is because the Torah forbids only a Beis ha'Kisei itself, or filth itself, like excrement. When there is no excrement there, it is forbidden only mid'Rabanan. We asked whether or not we are concerned for disgrace. This is an unresolved question about a mid'Rabanan law, so we are lenient about a Safek. A support is that we forbid while facing an old Beis ha'Kisei, but not while facing a new Beis ha'Kisei. Even inside a new Beis ha'Kisei is permitted.

Bi'ur Halachah (OC 83:1 DH v'Yir'eh): Panim Me'iros (1:87) says that a clean Beis ha'Kisei is forbidden only mid'Rabanan. He overlooked R. Yonah DH v'Davka, the Beis Yosef and all the Poskim. To avoid a contradiction in R. Yonah, the Acharonim explain R. Yonah's words (in DH v'Hazmanah) 'when there is no excrement there, it is forbidden only mid'Rabanan' to discuss a new Beis ha'Kisei.

Rosh (Berachos 3:57): The Torah forbids (Divrei Kedushah) only in an old Beis ha'Kisei. In a new Beis ha'Kisei without excrement, the Isur is only mid'Rabanan. The Gemara did not resolve whether or not we are concerned for Hazmanah. However, Rav Chisda permitted while facing a Beis ha'Kisei without excrement inside, and we established this to discuss a new Beis ha'Kisei. This implies that inside is forbidden.

Igros ha'Ramah (53): Rava admits regarding Guf Kedushah (something that has intrinsic Kedushah) that Hazmanah is significant.

Ohr Some'ach (Hilchos Tefilin 4:9 DH Ach): This is when the Kedushah cannot be redeemed. This excludes matters such a Beis ha'Keneses. Even though it is Guf Kedushah, if it is sold, the Kedushah is uprooted.

Poskim

Shulchan Aruch (OC 83:1): One may not read (Kri'as Shma) facing an old Beis ha'Kisei, even if the excrement was removed.

Mishnah Berurah (2): The Torah forbids regarding an old Beis ha'Kisei, so if it is a Safek whether or not it is old, one must be stringent.

Shulchan Aruch (2): If one prepared it for a Beis ha'Kisei, but did not use it yet, one may read facing it, but not in it.

Beis Yosef (DH Keshem): The Rif did not mention Ravina's question. This connotes that he holds that we are lenient. We have no source to say that there is Hazmanah.

Bach (3): In our text of the Rif, he brings the question of Hazmanah, and the Rosh and R. Yonah derived from the Rif's wording that he is lenient about it!

Bach (2): Ravina asked only about whether there is a Yad. However, if he said 'and this one also', surely it is forbidden due to Hazmanah.

Beis Yosef (DH Aval): R. Yerucham said that the Rosh is lenient (about Hazmanah, like the Rif), for he saw that the Rosh explained the Rif. He ignored the Rosh's final words, in which he learns from Rav Chisda. This is astounding. R. Yerucham himself initially said that the Rosh is stringent! Also the Rambam permits only facing a new Beis ha'Kisei, but not inside. We follow the Rambam and Rosh.

Magen Avraham (2): 'Inside' means within the walls, if it has walls.

Gra: The Shulchan Aruch is like the Rambam, who holds that whenever it says 'if you will say that...', this is the Halachah. Also, we say that Rav Chisda permits reading while facing a new Beis ha'Kisei. This implies that inside is forbidden. The Rosh says so. One need not say so. If so, the question returns: Ravina can learn from Rav Chisda that one may not pray inside! Rather, we must say that Rav Chisda was unsure (about inside).

Mishnah Berurah (6): If it was used even once, it is considered an old Beis ha'Kisei in every way, since there was Hazmanah and an action. If there was no Hazmanah, just once a person happened to eliminate there and the excrement was removed and there is no smell, it seems that it is not a Beis ha'Kisei at all, and even inside is permitted. Yevaser Tov says so.

Mishnah Berurah (7): One may read while facing it, even within four Amos.

Mishnah Berurah (8): Even though we hold that Hazmanah is not significant, one may not read inside, for this is very disgraceful to Kri'as Shma or Tefilah. Even b'Di'eved, he was not Yotzei.

Mishnah Berurah (9): If there are no walls, only the designated place is forbidden. If there are walls, the entire area within the walls is forbidden. Right outside is permitted. Be'er Heitev and Eliyahu Rabah permit thinking about Torah in a new Beis ha'Kisei that was not yet used. Surely, those who build it may not bless any Berachah within the walls, even before they built the walls, since they were authorized to build there. The place was designated for a Beis ha'Kisei, and it is forbidden.

Bi'ur Halachah (DH Hizmino): There is no distinction whether the Hazmanah was verbal or through an action. Seemingly, the designation must be permanent. Temporary Hazmanah is not Hazmanah. We hold that even permanent Hazmanah is not significant. We forbid here only due to disgrace, since the area was given a repulsive name. If so, perhaps this is even if the Hazmanah was temporary. This requires investigation. Hazmanah and use forbid mid'Oraisa, but not if the Hazmanah was temporary. One-time usage without Hazmanah is less than Hazmanah without usage. Also, if usage alone would forbid, this forbids all the streets of Neharde'a! Yevaser Tov says so; it correct. The Torah commands to have a shovel (in an army encampment, to cover excrement). This connotes that even though a place was designated, after it is covered, one may speak Divrei Torah there. Why is covering better than removing it? Perhaps the Torah discusses without Hazmanah, for he knows that he will need to cover it. Alternatively, since everyone had a shovel to immediately cover his excrement, this is like the Magen Avraham says in 87:1 (that if one empties or cleans a potty immediately after every use, it is not forbidden). This is no worse than a place designated to bury a Mes with intent to re-inter the Mes elsewhere. The place is permitted (Tur YD 264).

Kaf ha'Chayim (5): Since it is an Isur mid'Rabanan, if one read there, b'Di'eved he was Yotzei. Some say that b'Di'eved one must say Shma again, but he does not pray (Shemoneh Esre) again, for we are lenient about Safek Berachos, unlike the opinion that even Shemoneh Esre must be repeated.

Kaf ha'Chayim (6): The Shulchan Aruch connotes that one may read right outside, even within four Amos. The Pri Megadim says so. However, the Drishah citing the Mordechai says that one must distance four Amos. Eliyahu Rabah says similarly, but he is lenient b'Di'eved.