(1) Now there happened to be there a certain base man, whose name was Sheva, the son of Bichri, a Benjamite; and he blew the shofar, and said, ‘We have no portion in David, and we have no inheritance in the son of Jesse; every man to his tents, O Israel.’ (2) So all the men of Israel went up from following David, and followed Sheva the son of Bichri; but the men of Judah clung to their king, from the Jordan to Jerusalem.

(15) And they came and besieged him in Abel of Beth-maacah, and they poured a ramp until it stood even with the outer wall; and all the people that were with Yoav battered the wall, to throw it down. (16) A wise woman called out from the city: "Listen! Listen! Please say to Yoav, 'Come close to here so that I may speak to you.’" (17) So he drew close to her; and the woman said: "Are you Yoav?" And he answered, "I am." Then she said to him, "Hear the words of your maidservant." And he replied, "I am listening." (18) Then she spoke, saying, "[Your men] should have spoken at the start saying, 'Let them inquire at Abel [about surrender],' for they would have made peace. (19) I represent the loyal faithful people of Israel. You are seeking to destroy a city in Israel? Why will you swallow up the heritage of the Lord?’ (20) And Yoav answered and said: ‘Far be it, far be it from me, that I should swallow up or destroy. (21) The matter is not so.  Rather, a man of the Mount Ephraim, Sheva the son of Bichri by name, has lifted up his hand against the king, against David; deliver him olone, and I will depart from the city.’ And the woman said unto Yoav: ‘Behold, his head shall be thrown to you over the wall.’ (22) Then the woman went unto all the people in her wisdom. And they cut off the head of Sheva the son of Bichri, and threw it out to Yoav. And he blew the shofar, and they were dispersed from the city, every man to his tent. And Yoav returned to Jerusalem unto the king.

If a group of people is told by an attacking army, "Hand over one of your group and we will kill him; otherwise we will kill all of you," the group must allow itself to be killed and cannot hand anyone over.  If, however, the attacking army names a specific individual, just as they specified Sheva ben Bichri, the group may hand him/her over.

Rabbi Yehudah says that this is only true if that individual was also within the group and therefore he would have ended up being killed had they not handed him over.  If however he is outside the group, they may not hand him over.

It was taught: If a group of people were traveling and they chanced upon a marauding army which demands of them, "Hand over one of your group, or we will kill all of you," you may not hand anyone over, even though all will end up being killed.  If however they specify an individual, you may hand him over, as was the case of Sheva the son of Bichri.  Rabbi Shimon ben Laskish says that the case of Sheva the son of Bichri was different since he was liable for the the death penalty.  Rabbi Yochanan says that even had he not been liable for the death penalty, [he could have been handed over].

If a non-Jew says to a group of Jews, "give us one of your group, and we will kill him and if not we will kill all of you," you may not hand anyone over.  If, however, they specify an individual, you may hand him over.  (Tosefta in Terumot and Maimonides)  And there are those that say that even if they specify an individual you may not hand him over unless he is liable for the death penalty. (Bais Yosef quoting Rashi and the Ran)

 ...And how do we know this of murder itself [that one must allow himself to bekilled instead of killing another]? — It is common sense. Even as one who came before Raba and said to him, 'The governor of my town has ordered me, "Go and kill so and so; if not, I will kill you"'. He [Raba] answered him, 'Let him rather kill you than that you should commit murder; who says that your blood is redder? Perhaps his blood is redder.'

(12) Similarly, women who have been told by non-Jews, “Give us one of you that we may defile her; for if not, we will defile you all,” let [the non-Jews] defile them all, and do not hand over to them one soul from Israel.

Rav Huna said, "One may save himself from a murderer who is a minor."  We see that Rav Huna holds that we do not have to warn a murderer [that he may be killed in response to his attempted actions] regardless if he is an adult or a child.  Rav Chisdah asked a question to Rav Huna: "If its head was already delivered, you can't touch it since you can't kill one soul to save another."  And [according to Rav Hunah] how come?  This [fetus/child] is a murderer?  [Answer:] That case [where the head had already been delivered] is different since it is heaven who is threatening the woman's life.

Its head was already delivered: With a women that is experiencing difficulty giving birth and is in [mortal] danger. And it is taught in the first section [of this teaching], "the midwife extends her hand and cuts it up and extracts [the pieces];" as the entire time that that it has not gone out into the air of the world, it is not [considered] a soul, and [so] it is possible to kill it and to save its mother. But when its head came out, we cannot touch it to kill it, as it is like a born [baby]; and we do not push off one soul for the sake of another. And if you will ask [from] the story of Sheva ben Bichri - [wherein it is written] (II Samuel 20:21), "behold, his head is sent to you" - they pushed off one life for the sake of another; there, it was because even if they had not delivered him, he would have been killed in the city when Yoav would have seized it, and they would have been killed with him. But if he would have [otherwise] been saved - even though they would have been killed - they would not have been allowed to deliver him [to Yoav] in order to save themselves. And also (another answer) is that it is because he was a rebel to the kingdom, and so is it explained in the Tosefta (of Terumah).