Isaiah has been called "The Evangelical Prophet," because of his abundant predictions concerning the Messiah, his birth, his character, ministry, passion, death, his final victory and the majesty and glory of his kingdom. Nephi, who lived long before the Advent, delighted in the study of these themes. And it was necessary to study them in order to prove their truth to others.
The Law of Moses was given for the same purpose. To explain the Gospel of Christ. Refers especially to the ceremonial law. The dedication of the firstborn (Ex. 12:2); the distinction between clean and unclean food; the rules for purification; lawful and unlawful marriages; the laws regarding priestly orders, holy places, times of holding services; the Sabbath, the sabbatical year (every 7th); the year of jubilee; passover; the feast of weeks; of tabernacles of trumpets, and the day of atonement. All such precepts were given for the purpose of teaching the children of Israel the first principles of the Gospel.