As Nephi feels the weight of his divine responsibility and the pressures of the failure of his people to see what was plainly before them, in the midst of a righteous and prophetic despair, God blesses Nephi and gives him great power. What an unexpected timing! Right when Nephi is certain that he is failing, God not only confirms his efforts, but blesses him for it in ways that are hard to comprehend.
To this man who has already been sufficiently prophetic that he could “see” the hidden murderer, God gives him a blessing that will last “forever.” God “will make [him] mighty in word and in deed, in faith and in works.” Most importantly, God grants to him: “even that all things shall be done unto thee according to thy word, for thou shalt not ask that which is contrary to my will.”
This appears to be parallel to a promise made Joseph Smith:
Doctrine and Covenants 88:64-65
64 Whatsoever ye ask the Father in my name it shall be given unto you, that is expedient for you;
65 And if ye ask anything that is not expedient for you, it shall turn unto your condemnation. (see also DC 11:14;
There are two parts to the promise. One is that the prophet is given power to effectively ask. That is, the asking will create the result asked for. However, this is not without agency and responsibility. When the Lord gives this gift to Nephi he emphasizes that it comes as a result of God’s trust. Surely that trust was also part of the promise to Joseph, but that later promise also shows that the use of such power from God also carries a responsibility. To use it unwisely is an inextricable aspect of agency. However, should that happen, consequences would attend, and as one might imagine, they would be dire indeed.