Helaman 10

Knowing Nephi's great faithful, while being discouraged, the voice of the Lord came saying -

"Blessed art thou, Nephi, for those things which thou hast done; for I have beheld how thou hast with unwearyingness declared the word, which I have given unto thee, unto this people. And thou hast not feared them, and hast not sought thine own life, but hast sought my will, and to keep my commandments.
5 And now, because thou hast done this with such unwearyingness..." (Book of Mormon | Helaman 10:4 - 5)

The blessing was -

"...I will bless thee forever; and I will make thee mighty in word and in deed, in faith and in works; yea, 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." (Book of Mormon | Helaman 10:5)

It is important to understand that with this great promised blessing, the Lord knew that Nephi would not do anything that the Lord would not have him do. This would suggest that Nephi had progressed to the point that he preceived a greater purpose and the ways of the Lord -

"For my thoughts are not your thoughts, neither are your ways my ways, saith the LORD.
9 For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts." (Old Testament | Isaiah 55:8 - 9)

In other words, Nephi understand when his power should be done, especially with the wicked in general with famine, pestilence, and destruction. But even of a greater blessing, Nephi received the "sealing" power much like Peter where -

"...I give unto you power, that whatsoever ye shall seal on earth shall be sealed in heaven; and whatsoever ye shall loose on earth shall be loosed in heaven; and thus shall ye have power among this people." (Book of Mormon | Helaman 10:7)

Nephi, knowing the will of the Lord, did not yet exercise this power of calamnity but called all people to repentance even to the point -

"...the power of God was with him, and they could not take him to cast him into prison, for he was taken by the Spirit and conveyed away out of the midst of them." (Book of Mormon | Helaman 10:16)

Knowing that the Lord had given him this power the Lord knew he would not exercise that power contrary to His will. This becomes evident at the point that it seemed the people were nearly ripe in inquity, Nephi did not immediately on his own accord exercise this power but instead prayed -

"O Lord, do not suffer that this people shall be destroyed by the sword; but O Lord, rather let there be a famine in the land, to stir them up in remembrance of the Lord their God, and perhaps they will repent and turn unto thee." (Book of Mormon | Helaman 11:4)

This is an important principle. Even though Nephi posessed this priesthood power, he chose to pray for guidance to know the Lord's will. This is a pattern that should be followed by all who hold the priesthood.