(Rav Yehudah): If Shelamim was slaughtered before the gate of the Heichal was opened, it is Pasul. It says "u'Shchato Pesach Ohel Mo'ed", i.e. when it is open, but not when it is locked.

Clearly, if the door is shut, this is like being locked.

Shabbos 106b (Mishnah): If a deer entered a house and one locked the door, he is liable.

If Reuven sat in the doorway and did not fill it, and Shimon sat (next to him) and filled it (trapping a deer in the house), Shimon is liable;

If Reuven sat in and filled (the width of) the doorway, and Shimon sat next to him (and also filled the width), even if Reuven left and Shimon remained, Reuven is liable and Shimon is exempt. Shimon is like one who locked his house to guard the contents, and a deer was found inside.

(R. Aba): If a bird entered under the corner of one's garment (and trapped itself, on Shabbos), one may guard it until Motzei Shabbos.

Question (Rav Nachman bar Yitzchak - Mishnah): If Reuven sat in the doorway and filled it, and Shimon sat next to him, even if Reuven left and Shimon remained, Reuven is liable and Shimon is exempt.

Suggestion: Shimon is exempt, but it is forbidden to remain!

Answer: No, he is exempt and permitted (to do so).

Support (Seifa): (Shimon) is like one who locked his house to guard the contents, and a deer was found inside.

This shows that he is exempt and permitted.

Rif and Rosh (Shabbos 38a and 13:2): If (a deer entered the house and) Reuven filled the doorway, and Shimon sat next to him, even if Reuven left and Shimon remained, Reuven is liable and Shimon is exempt. It is even permitted for Shimon.

Ran (DH l'No'el): Shimon is like one who had a deer in his house and the door was closed and it is guarded through this, and he locked the door. Even though he increased the guarding, it is permitted. We do not say that it is as if he trapped it, for had he not locked it, perhaps the door would have opened and the deer would have escaped. So too, Shimon may sit next to Reuven, since Reuven already filled the opening, even though after Reuven left it is guarded due to Shimon. Alternatively, if a deer was tied up in a house and one locked the door, even if the deer was later untied, we do not say that he must open his houseto let the deer out, since when he locked it it was permitted. Likewise, Shimon need not get up after Reuven leaves. The Rashba explains like this.

Ran (ibid., citing the Rashba): It seems that the Yerushalmi permits to lock one's house to guard it, even if a deer is inside. Since he must guard his house, even though automatically the deer will be trapped, it is permitted, as long as he does not intend to guard just the deer. It teaches this with a Heter to raise a drowning child from the river on Shabbos and fish with him, and to excavate a fallen house to save someone and take gold coins at the same time.

Rebuttal (Ran): How can we permit when he intends also to trap the deer? Will we permit a Melachah just because he needs to lock his house? I say that even if he did not intend to lock for the sake of the deer, but he knows that it is there and it will surely be trapped, it is forbidden. In all of Shabbos we say that R. Shimon (who permits something that one does not intend for) admits about a Pesik Reishei (an inevitable consequence. It is as if he intended.) The Yerushalmi means that if he did not intend to trap the deer at all, and later he found out that it is inside, he need not open the house. We support this from saving the child or excavating the house. They are not identical. There, he intends for Heter along with Piku'ach Nefesh. The Bavli says like this in Yoma (84b). Since the Melachah is an obligatory Mitzvah upon him, even if he intends for another Melachah with it, and the latter is forbidden on Shabbos, Chachamim permitted lest he refrain from Piku'ach Nefesh obligatory on him. Heaven forbid that we would permit an Isur along with a Melachah of Reshus! This is why regarding the deer the Yerushalmi says 'he intended to lock it (his house) and he locked it and in front of the deer.' Regarding the child it says 'he intended to raise him and to raise...' They are brought together because in both cases a forbidden Melachah is done with a permitted Melachah, but they are not the same principle.

Shiltei ha'Giborim (Shabbos 38a): The Rashba holds that even though a Pesik Reishei is forbidden, when one does a permitted act with it and intends also for the Heter, it is permitted even if he also intends for the inevitable consequence. I wrote that if something can be done without a Pesik Reishei, it is permitted even if he does it with a Pesik Reishei. This follows from a Kal va'Chomer from the Rashba.

Rambam (Hilchos Shabbos 10:23): If a deer entered a house and one locked the door, he is liable. If two people locked the door, they are exempt. If one could not lock it and two people locked it, they are liable. If Reuven sat and filled the doorway, and Shimon sat next to him, even if Reuven left, he is liable and Shimon did not do anything. Shimon may remain there until evening and take the deer. He is like one who looked his house to guard the contents, and a deer was found guarded inside. He did not do anything.

Magid Mishneh: The Ramban says that the Tosefta connotes that he locked his house to guard it, and did not know at all that there is a deer inside, and not it is guarded inside. He may leave it locked until night. The same applies if he sat in the opening, and a deer was found to be inside. He may stay there, for the trapping preceded the intent. The Rashba says that the Yerushalmi connotes that it is permitted even if he intends for both. One should not be so lenient.

Shulchan Aruch (OC 316:5): If a deer entered a house and one locked the door, he is liable.

Avnei Nezer (OC 192): He is liable even for closing the door without locking it. This is logical. Even though 'Na'al' always connotes that with a lock, like the Yerushalmi says, the Rashba and Ran say that it is trapped merely through closing the door. Also Zevachim 55a says that closed is like locked. This shows that they are different. If the Mishnah means 'closed', why does it say 'locked'? It seems that regarding a deer, which cannot open a closed door, it is as if it is locked.

Bi'ur Halachah (DH Chayav): He is liable only if he knew at the time the locked it that there is a deer inside. If he found out only later, he is exempt. This is like one who intended to pick up detached Peros, and he cut attached Peros. This is Ohnes. Later he may intend not to open it until evening. The same applies when he sat in the opening unaware that there is a deer inside, for he did not intend for the deer until later. A Tosefta clearly says so. I do not know why the Rashba was unsure about this.

Rema: If the door was already closed, one may lock it with a lock.

Mishnah Berurah (23): Since it cannot escape, locking it is merely guarding it. It is not trapping, for it is already trapped.

Shulchan Aruch (6): If Reuven sat and filled the doorway, Shimon may sit next to him. Even if Reuven left, Shimon is exempt and permitted, and Reuven is liable.

Tosfos Yom Tov (Shabbos 13:7 DH Af): We must say that Reuven entered the house. If not, not, how can Shimon fill the place without there being an empty space in between? When there is a space, the deer is not trapped, so when Shimon returns and fills the opening, he traps the deer, and he would be liable!

Rebuttal (Magen Avraham 11): If one has a chicken in his house, and a door was opened, is it forbidden to close it?! Surely it is permitted! We must say that since it was already trapped, it is permitted. The same applies here. Rashi says that he is like one who merely guards a deer that he had from yesterday. I say that the Ran's words deceived him. The Ran only intended to say that when he merely increases guarding it is permitted, and all the more so when he does not increase anything. The Ran held that the Mishnah would not need to teach this. When he said that the deer was tied and one locked the door, this is when it was not yet locked when the deer was tied.

Kaf ha'Chayim (40): The Magen Avraham connotes that if the house was once locked after the deer was tied, even if later both were opened, he may lock the house again. The Acharonim refuted this from the Tosefta that obligates one who locks it again even if the deer was previously trapped.

Mishnah Berurah (25): It is permitted when Shimon does not move at all when Reuven left, e.g. Reuven entered the house, or Shimon was in the space of the opening from the inside and Reuven was in the space of the opening from the outside, and left. Shimon may remain, for he did not do a new act. He merely guards a deer that was already trapped. If Shimon was on the outside and he needed to move to allow Reuven to leave, the deer ceased to be trapped, and if Shimon returns to his place he is liable for trapping. One may not lock his house if he knows that there is a deer inside, even if he does not intend to trap it, for it is a Pesik Reishei and the Torah forbids it, and all the more so if he intends also to trap it.

Kaf ha'Chayim (41): One may not close a room if there is a cat inside (that will be trapped).

Kaf ha'Chayim (43): The Ramban permits sitting next to Reuven even if he intends to guard the deer.

Bi'ur Halachah (DH Yashav): If one forgot that it is Shabbos or that trapping is forbidden and sat in the opening, and later remembered, I am unsure if he may stay there until dark. He already transgressed, and leaving will not fix this. The Rashba said 'since he did not transgress mid'Oraisa' implies that if he transgressed mid'Oraisa, he may not stay there.