After the requisite soul-searching and angst and all that, Nephi cut off Laban’s head, snicker-snack. He probably did not know at the time that he was setting up a type of Christ.

Nephi offered—or rather the Holy Ghost did—this justification for killing the man:

It is better that one man should perish than that a nation should dwindle and perish in unbelief.

Scripture records another occasion when the Holy Ghost inspired a man to speak similar words.

And one of them, named Caiaphas, being the high priest that same year, said unto them, Ye know nothing at all,
Nor consider that it is expedient for us, that one man should die for the people, and that the whole nation perish not.
And this spake he not of himself: but being high priest that year, he prophesied that Jesus should die for that nation.

Neither Nephi nor Caiaphas’ audience react as if the concept had a paradigm-shattering novelty. The fact that its brought up both times in what is basically a legal argument suggests that it was a principle of Jewish law. I would be surprised if it weren’t. Every functioning system of law has to have escape valves that set aside normal rules for extreme emergencies. Ours does it with the principle that the Constitution-Is-Not-A-Suicide-Pact and with judicial and especially executive discretion. (For instance, back in the Bush years there was this lively internet debate over whether it would be moral or legal to torture a terrorist to reveal where he’d hid a nuclear bomb. In reality, if that scenario actually ever happened, whoever performed the torture would be got off on a technicality by the courts or would be quietly pardoned by the President).

And, in fact, it appears that it is a principle of Jewish law. An internet entity over at the Mormon Dialogue board has the Rabbinic goods.

“R. Nahman b. Isaac said: A transgression performed for the sake of heaven is better than a precept performed not for the sake of heaven.”
Jael, wife of Heber the Kenite, is famous for having slain the Canaanite general Sisera when he sought refuge in her tent. Not only might this be construed as breaking the commandment against killing, the sages sensed that something more had occurred.
“Blessed above women shall Jael be, the wife of Heber the Kenite…
R. Johanan said: [Sisera] that wicked one had intercourse seven times [with Jael] at that moment, as it says: “At her feet he sunk, he fell, he lay;” etc…”
These verbs were understood as euphemisms, and their appearance for a total of sevens times meant that Jael had gone to bed with Sisera not once, but seven times.
As Rashi explained, “Blessed [is Jael] for having committed a sin for the sake of heaven in order to sap that wicked one’s strength so that she could slay him.”
“Both Tamar and Zimri committed adultery. Tamar committed adultery and gave birth to kings and prophets. Zimri committed adultery and on his account many tens of thousands of Israel perished.”

****

The man had been whipped by R. Shila for sleeping with a gentile woman. The man decided to inform upon the rabbi to the Persian authorities that he had applied punishment without sanction, so R. Shila put him to death to prevent that. The Talmudic discussion cites the principle of preempting those who would seek your life (pursuers), by killing them first. The whole history of silencing informers is a dark, but fascinating and little-known subject in Judaism. It lasted well into the 19th century, with victims perhaps numbering in the hundreds throughout Eastern Europe. These secret Jewish courts form the historical kernel of what would later be used for that vile fabrication- the Protocols of the Elders of Zion.

Here’s Walsh, in a similar vein:

The Old Testament lays a narrative groundwork for the legal view that, under rare appropriate circumstances, a single person can be exposed to certain death for the benefit of the whole. David Daube has shown that in early Israel there was little moral constraint protecting the individual in such a case:
Clearly, no such scruples are entertained by the Judeans in Judges [15:9–13] who, fearing what their mighty Philistine neighbours might do to settle accounts with the indomitable Samson, propose to deliver him up in fetters.35
And the case of Sheba, a rebel against King David in 2 Samuel 20, provided a further instance where peace was offered to an entire city in exchange for the life of a single man (2 Samuel 20:21–22).
This point of law, along with its biblical precedents and ethics, was hotly debated between the Pharisees and Sadducees at the time of Christ: The initial position of the Pharisees was “unbendingly negative: no one to be surrendered ever, even though extinction will ensue,”36 while the Sadducees (notably Caiaphas in condemning Jesus) were more liberal (John 11:50; 18:14).37 Eventually the view of the Sadducees prevailed, as evidenced in the Genesis Rabba: “It is better to kill that man [Ullah] so that they may not punish the congregation on his account.”38 In the rabbinic period, Talmudic law went on to puzzle deeply over the meaning and implications of these notions. Used judiciously, these debates confirm the fact that surrendering one person to be killed for the benefit of the entire group was a topic addressed in biblical law.
In the Talmud, unpremeditated homicide was eventually subdivided into five categories: negligent, accidental, nearly avoidable, under duress, or justifiable.39 For purposes of comparison with Nephi’s case, justifiable killings included (1) those that prevented one man from killing another (and by analogy, Nephi’s slaying of Laban prevented him from causing Lehi’s people to perish spiritually) and (2) surrendering a specific named individual to be killed when heathens threaten to kill a whole group unless that one is delivered up.40 While the rabbis passionately and compassionately debated the limited circumstances under which the life of a specified individual could be sacrificed for the benefit of the group,41 and whereas one case from the fourth century A.D. distinguished between an individual and a group ordered to put a man to death (the individual must first offer himself to be killed),42 there can be little doubt that the possibility of killing one person for the benefit of the whole was recognized under early Jewish law and that it was consonant with the rationale expressly stated in Laban’s case (“better that one man should perish than a nation should dwindle and perish in unbelief,” 1 Nephi 4:13).

Christ completely fulfills this law. The law points to Christ.

So in fact Laban is a type of Christ. So would anyone be who was killed according to this precept of Jewish law. But with Laban there is more. His blood redeems a nation (from sin), but specifically it saves Nephi’s life and his honor. Nephi swore a terrible oath by God and by his own life that he would get the brass plates. Without Laban’s death, Nephi likely would have died trying and would be an oathbreaker. Laban’s death save’s Nephi’s life and Nephi’s soul. Laban reflects that the national salvation Christ would offer, which the Jews expected, would also be an individual and personal salvation. Christ would redeem his people by redeeming each of his people. (Notice how Nephi himself benefits from the brass plates in subsequent chapters).

There are other parallels. Nephi’s salvation is to take on him the name of the person who died. Nephi’s salvation is to clothe himself in the garments of the one whose death saves his nation. Laban’s death alone does not save Nephi. Nephi must become Laban to benefit from it.

Further, Nephi must actively endure in that identity. The name-taking and the robing is not symbolic only. He must act.

What’s the significance of this? The apologetic significance is that the Book of Mormon is quite a complex document, both in judaic terms and in doctrinal and symbolic ones. The doctrinal significance is the centrality of Christ to everything.

There is another possible doctrinal significance which is also a very personal significance. When we’re in a middle of a trial, we should not expect to understand fully why it’s happening. Nephi had no notion that he was making a prophecy of Christ. When we say ‘why, God’, even if we should receive an answer, we should remember that the fulness of times is not yet. We do not see the end from the beginning.

We should also remember that we can’t confine the Lord to Sundays or to conventional expressions of piety. He works through Laban, through the Assyrians, through Satan, to achieve his purposes. Remember the walls of the Nauvoo temple being ornamented with crushed china? God builds his house with broken vessels.

All that said, we are still left with the basic unease that God made drunk and murderous Laban, or adulterous Jael, his types and symbols.

Let’s think about the atonement. One longstanding explanation for the atonement is the ransom theory, not without support in scripture, that Christ bought us from Satan by offering Satan power over Himself. There is also evidence in scripture that Christ’s atonement involved a kind of communion with each person’s suffering. Cite. Would it also involve Satan forcing on Christ a kind of communion with each person’s sins? Christ tasting wickedness and wrongness would be more satisfying to Satan than just pain or grief. If so, then the dying Christ is the type of every sinner–He descends below all things—and the connection between a Laban or a Jael and Him is right.

Go a little further. The sum of all sins is Satan’s identity. So in forcing Christ to take them all on, Satan was robing Christ as himself and giving Him his name. Little wonder, then, that the gates of hell cannot stand against him and that Christ can pass by the guardians there to carry out whatever treasure He likes.