Nephi’s favorite prophet, Isaiah, is famous for a pattern of Hebrew poetry called parallelism. Nephi emulates this in many of his passages including these verses. Of Hebrew poetry, Victor Ludlow writes:
“Parallelism is the most distinctive quality of Hebrew poetry, and it is found in most of the famous biblical passages. In parallelism, a thought, idea, grammar pattern, or key word of the first line is repeated or continued in the second line. There are two basic types of parallelism, grammatical and semantic. Grammatical or ‘form’ parallelism is often difficult to identify, especially in non-Hebrew translations, because the rhyme schemes, grammar forms, conjugation patterns, prefix or suffix parallelisms, and so on may not carry over into the new translation. However, semantic parallelism is more easily recognized in English and other non-Semitic language translations since it is a ‘theme rhyme’ or ‘idea pattern’ in which the thought or meaning in one line is related to an idea of another line in a variety of parallel patterns.” (Isaiah: Prophet, Seer, and Poet, p. 32)
He goes on to describe seven different types of semantic parallelism. The passage in question exhibits two of these types.
a) For my soul delighteth in the scriptures,
b) and my heart pondereth them, and writeth them for the learning and the profit of my children.
a) Behold, my soul delighteth in the things of the Lord;
b) and my heart pondereth continually upon the things which I have seen and heard.
These passages exhibit synthetic parallelism and synonymous parallelism. In synthetic parallelism, “the second line completes or complements the thought of the first in a variety of possible combinations…An idea is introduced in the first line, which is incomplete or generates questions about that idea. The second line then completes the idea, or answers a question raised by the first line.” (Isaiah: Prophet, Seer, and Poet, pp. 33-4) In verse 15, the first thought, my soul delighteth in the scriptures, is completed in the second line, and my heart pondereth them and writeth them for the learning and profit of my children.
In synonymous parallelism, “a theme of the first line repeats itself in the second line, but in slightly different words.” (Isaiah: Prophet, Seer, and Poet, pp. 32) The ideas in verse 15 are repeated in verse 16 with slightly different concepts. The phrase, ’For my soul delighteth in the scriptures‘ is repeated in verse 16 as ’my soul delighteth in the things of the Lord
In The Encyclopedia of Mormonism, another poetic style is discussed—that of chiasmus, or the repeating of concepts in the reverse order in which they were presented. This pattern is described as following the general patterns (a-b-b-a), (a-b-c-c-b-a), etc:
"In the Psalm of Nephi (2 Ne. 4:15-35), the initial appeals to the soul and heart are accompanied by negations, while the subsequent mirror uses the heart and soul are conjoined with strong affirmations, making the contrasts literarily effective and climactic:
A) Awake, my soul! No longer droop in sin.
B) Rejoice, O my heart, and give place no more for the enemy of my soul.
C) Do not anger again because of mine enemies.
C) Do not slacken my strength because of mine afflictions.
B) Rejoice, O my heart, and cry unto the Lord, and say:
A) O Lord, I will praise thee forever; yea, my soul will rejoice in thee, my God, and the rock of my salvation. [2 Ne. 4;28- 30.]" (The Encyclopedia of Mormonism, edited by D. Ludlow, p. 182)