"Sanctified unto us for righteousness"

Given the fact that Lehi's group left Jerusalem around 600 BC, you would think that their religious writings would read much like the Old Testament. That is only partly the case. Critics have argued that it reads too much like the New Testament. There are numerous examples on this blog showing how the Book of Mormon fits an ancient Israelite worldview. Still, it is true that the Book of Mormon "talk[s] of Christ, [...] rejoice[s] in Christ, [...] preach[es] of Christ [and] prophes[ies] of Christ" (2 Nephi 25:26), something that we don't see much of in the Old Testament in such a straight-forward manner.

There are theories postulated that our current Old Testament has been highly influenced by King Josiah and the so-called Deuteronomic reforms. Before these reforms, the ancient Israelites had a richer temple worship including a Heavenly Mother and the Son of God, among other things. King Josiah was primarily concerned with the Law (of Moses). Margaret Barker and other scholars argue that the former theology was not completely forgotten and is one of the reasons why Christianity could be accepted and spread like it did. This Deuteronomist thinking and theology is still prevalent today among orthodox Jews. They interpret the tree of life as the Torah (the Law). 

Interestingly, the Nephites actually explain why the Book of Mormon reads like an Old/New Testament hybrid themselves. Their explanation fits very well into the paradigm briefly laid out in the previous section and explained in more detail in the link I gave.

24 And, notwithstanding we believe in Christ, we keep the law (Torah) of Moses, and look forward with steadfastness unto Christ, until the law (Torah) shall be fulfilled.
25 For, for this end was the law given; wherefore the law (Torah) hath become dead unto us, and we are made alive in Christ because of our faith; yet we keep the law (Torah) because of the commandments. (2 Nephi 25)

For Deuteronomists as well as believing Jews today, the Torah seems to be considered an end goal in itself. Lehi and Nephi's views came from an older tradition, where the Torah was just the means to an end. The end was the Son of God, the Messiah, Christ who should redeem them and who the law was pointing to. They brought this tradition with them to the promised land and taught their children about it. There is a similar sentiment in Jacob 4

4 For, for this intent have we written these things, that they may know that we knew of Christ, and we had a hope of his glory many hundred years before his coming; and not only we ourselves had a hope of his glory, but also all the holy prophets which were before us.
5 Behold, they believed in Christ and worshiped the Father in his name, and also we worship the Father in his name. And for this intent we keep the law of Moses, it pointing our souls to him; and for this cause it is sanctified unto us for righteousness, even as it was accounted unto Abraham in the wilderness to be obedient unto the commands of God in offering up his son Isaac, which is a similitude of God and his Only Begotten Son.

Jacob talks about the holy prophets that lived before and their hope in Christ. This is an ancient tradition and goes all the way back to Adam as we read in the Pearl of Great Price, even though it was corrupted and lost several times throughout history. Jacob clearly also views the law of Moses as a means to a higher end. That does not mean he does not keep it. It was important for the Nephites to keep the law but the reason for doing so was completely different from the Deuteronomists. When the Nephites kept the law of Moses with the intent to have their souls pointed to Christ, the law was sanctified unto them for righteousness.

I find that phrase intriguing. The law in itself is dead according to Nephi, but it is sanctified for them when they use it as a vehicle to come unto Christ. We do not live the law of Moses anymore. It was replaced by a higher law. Does that mean we got better commandments now? Commandments that can actually bring salvation unlike the "dead" law of Moses? No. If we let any commandment be an end in and of itself, we make the same mistake as the Jews. 

8 For behold, the covenant which I have made with my people is not all fulfilled; but the law which was given unto Moses hath an end in me.

9 Behold, I am the law, and the light. Look unto me, and endure to the end, and ye shall live; for unto him that endureth to the end will I give eternal life.

10 Behold, I have given unto you the commandments; therefore keep my commandments. And this is the law and the prophets, for they truly testified of me. (3 Nephi 15)

These are the words of the Savior. My conclusion from these verses is that even though we don't follow those weird rules in Leviticus and Numbers, nothing else has changed much. We are still asked to keep the commandments in verse 10, but the reason for that is clear: They testify of Him. They bring us to Him. He is the law. If we let the commandments point our souls to the Savior, they are "sanctified unto us for righteousness". It is not only the law of Moses that point our souls to Him. 

Behold, my soul delighteth in proving unto my people the truth of the coming of Christ; for, for this end hath the law of Moses been given; and all things which have been given of God from the beginning of the world, unto man, are the typifying of him. (2 Nephi 11:4)

All things given by God point to him. Anything that we treat as an end goal instead of a gateway to Christ becomes "dead". As Nephi stated, we are made alive in Christ.

This is expressing New Testament views in Old Testament times. Testament means covenant and Christ is the mediator of the new covenant (Hebrews 9:15). Lehi and Nephi coming from an Israelite culture in 600 BC Jerusalem, having a pre-Deuteronomist belief that they passed on to their children in the Americas, explains perfectly well why the Book of Mormon is written the way it is.