Chiastic structures in 3 Nephi 5

In 3 Nephi 5, Mormon, who has abridged the records on the large plates of Nephi thus far, introduces himself properly for the first time. Doing so, he seems to get in a rather poetic mood. The poetic parallelism in verse 21 sounds like something taken straight from Isaiah

Surely he hath blessed the house of Jacob, and hath been merciful unto the seed of Joseph.

But as I read on, I found this to be the opening part of a chiasmus

A. Surely he hath blessed the house of Jacob, 

   B. and hath been merciful unto the seed of Joseph. 

      C. And insomuch as the children of Lehi have kept his commandments he hath blessed them and prospered them according to his word.

   B'. Yea, and surely shall he again bring a remnant of the seed of Joseph to the knowledge of the Lord their God.

A'. And as surely as the Lord liveth, will he gather in from the four quarters of the earth all the remnant of the seed of Jacob

The chiasmus builds up with the forefathers of the Nephites and is centered on the "children of Lehi". Mormon has just mentioned that he is a "pure descendant of Lehi". He is among the people at the center of the chiasmus and probably understands the importance of the work he is doing with preserving and writing on the plates. He knows that some day, the future "children of Lehi" will receive the knowledge of the Lord's covenants that will link them to their forefathers, Jacob and Joseph.

Notice also how A and B talk about the past of Jacob and Joseph, while their counterparts, A' and B', prophesy of their future.

Another interesting note: The center of the chiasmus is another quote from King Benjamin. Compare with Mosiah 2:22

if ye do keep his commandments he doth bless you and prosper you

There were probably many sermons that did not make it to the abridged version. Since Mormon included King Benjamin's entire talk, it must mean that it was regarded as pivotal in the Nephite heritage or that Mormon personally loved the talk, or both. So a reference by him makes sense. 

Reading that whole verse in Mosiah 2:22 clearly demonstrates another example of the Book of Mormon proverb. Quite fittingly, Mormon manages to put that into the center of the chiasm as well.

Since I already have downloaded a document showing poetic parallelisms in the whole Book of Mormon, I was curious to see if this one was included. Interestingly, it wasn't but the latter part was included as part of another chiasmus. That is, the A' from the chiasmus above is also the beginning of a new chiasmus that looks like this:

A And as surely as the Lord liveth,

   B will he gather in from the four quarters of the earth all the remnant of the seed of Jacob, who are scattered abroad upon all the face of the earth.

      C And as he hath covenanted with all the house of Jacob, 

         D even so shall the covenant wherewith he hath covenanted 

            E with the house of Jacob be fulfilled in his own due time, 

            E' unto the restoring all the house of Jacob unto the knowledge 

         D' of the covenant that he hath covenanted with them. 

      C' And then shall they know their Redeemer, who is Jesus Christ, the Son of God; 

   B' and then shall they be gathered in from the four quarters of the earth unto their own lands, from whence they have been dispersed; 

A' yea, as the Lord liveth so shall it be. Amen

C does not seem a great match until we realize that "they" in C' refers to the house of Jacob and "he" in C refers to Jesus Christ (see verse 20 in 3 Nephi 5). This makes C and C' a rather beautiful pair: Christ has covenanted with the house of Jacob and because of the covenant, one day the house of Jacob will know Christ, their Redeemer.

I am not sure if this overlapping chiastic structure even was a thing in ancient Hebrew poetry. Of course, you can never know for certain if a chiasmus was intentional or not, but I think both are pretty strong candidates. Maybe Mormon was just very clever?