Nephi served with such diligence that the Lord bestowed upon him great power. He was given power over the people and the elements of the earth. He was also granted a sacred bestowal of the sealing power, the same power held by Elijah the prophet: “The power of Elijah is the sealing power of the priesthood by which things that are bound or loosed on earth are bound or loosed in heaven (D&C 128:8–18)” (Guide to the Scriptures, “Elijah”).
President Joseph Fielding Smith (1876–1972) taught about the sealing power given to various prophets:
“The Lord conferred authority on some of his chosen servants and gave them exceptional powers. … In this manner Elijah obtained the keys of power in the priesthood to raise the dead, heal the sick, close the heavens that it did not rain only by his word, and for more than three years there was no rain, and moreover he had the power to call down fire from heaven to destroy the enemies of the Church. …
“The Lord gave similar authority to Nephi, son of Helaman, who likewise had authority to close the heavens and perform other mighty works, simply by his faith and the commandment from the Lord [see Helaman 10:7]. This wonderful power has been bestowed on but a few of the servants of the Lord” (Answers to Gospel Questions, comp. Joseph Fielding Smith Jr., 5 vols. [1957–66], 4:95).