In Alma 50:38-39, Mormon notes that Nephihah "had filled the judgment-seat with perfect uprightness before God. Nevertheless, he had refused Alma to take possession of those records and those things which were esteemed by Alma and his fathers to be most sacred; therefore Alma had conferred them upon his son, Helaman."
What is going on here? When and why did this happen? According to the text:
(1) Alma stepped aside to preach, and appointed Nephihah chief-judge in the ninth year (Alma 4:20). (2) Alma did not confer the records upon Helaman until after the seventeenth year had ended (Alma 35:12).
(3) Alma was taken up by the spirit near the commencement of the nineteenth year (Alma 45 18).
(4) Nephihah died in the twenty-fourth year (Alma 50:37, 40).
In view of these chronological facts, Cleon Skousen says the following:
We learn that when Alma knew he was about to terminate his mission in life, he had attempted to get the righteous Nephihah to be the custodian of the sacred library of the Nephites as well as the next historian of this people, but Nephihah had refused. This had compelled Alma to turn them over to his son, Helaman, even though he was very young for such a tremendous responsibility (Alma 36:3). [W. Cleon Skousen, Treasures from the Book of Mormon, Vol. 3, p. 3134]
We can guess from the data supplied above that one of the reasons that Nephihah turned Alma down might have been age or physical condition. Nephihah only lived six years after refusing to take the records. Perhaps he didn't believe that he would even live that long.
Another reason might have to do with what Nephihah had originally sworn to be responsible for. We know that Nephihah had "filled the judgment-seat with perfect uprightness before God" (Alma 50:37). We also get an idea of the responsibilities he had sworn to uphold by the words in Alma 50:39:
Behold, it came to pass that the son of Nephihah was appointed to fill the judgment-seat, in the stead of his father; yea, he was appointed chief judge and governor over the people, with an oath and sacred ordinance to judge righteously, and to keep the peace and the freedom of the people, and to grant unto them their sacred privileges to worship the Lord their God, yea, to support and maintain the cause of God all his days, and to bring the wicked to justice according to their crime.
Therefore, the second reason why Nephihah refused to take care of the plates might have been that the responsibility for keeping the Nephite records wasn't part of what the chief-judge was originally sworn to do. Perhaps he felt it wise to maintain that separation between church and state. What is important to keep in mind is that this was probably an honest search by two righteous men for a correct way to maintain the Nephite records rather than a drastic dispute over power. [Alan C. Miner, Personal Notes]