It is important to understand what is meant by the law as opposed to the prophets (see 3 Nephi 15:10). At the time of Jesus the Jewish scriptures (our Old Testament) were divided into three major sections. The Law, or the Torah, included the five books of Moses (Genesis, Exodus, Leviticus, Numbers, and Deuteronomy). The Prophets included the writings of the various prophets (such as Isaiah, Jeremiah, Ezekiel and Daniel). The third section, the Writings, included the historical books (such as Joshua, Judges, Samuel, Kings) and the poetic books (such as Psalms and Proverbs).
The prophecies and covenants given through the prophets but not fulfilled by the Atonement and Resurrection were not done away with, and are still in force. For example, the promises concerning the eventual gathering of Israel, its restoration to the lands of promise, and the events concerning the ushering in of the Millennium belong to the category Jesus called the Prophets. Some of these promises go all the way back to Adam. Enoch foretold many of them. They are involved in Abraham’s covenant. Moses himself gave many of the details concerning these prophetic promises. They also include teachings, such as the Ten Commandments, which never are done away with. Jesus repeated a portion of Malachi and told the Nephites to record it (see 3 Nephi 24–25). From this, Latter-day Saints know that the law of tithing was not a part of the law of Moses that was fulfilled in Christ, as some churches claim.
The law that was done away with in Christ was the strict ceremonies, observances, and offerings peculiar to the law of Moses. Thus Jesus could say, “For behold, the covenant which I have made with my people is not all fulfilled; but the law which was given unto Moses hath an end in me” (3 Nephi 15:8).
Note that it was Jesus who instituted, fulfilled, and announced the fulfillment of the law of Moses (see v. 5).