In this verse, Nephi speaks in the future tense: "I shall give commandment" (1 Nephi 6:6). Evidence that Nephi did indeed pass on this commandment can be found in Jacob 1:1–4, where Jacob gives more details about Nephi’s instructions and the sacred nature of the Small Plates. If you carefully read the rest of the writings on the Small Plates, you will see that Nephi’s instructions were followed by Jacob’s posterity. They passed the record down through their posterity, focused on things of spiritual significance, and only lightly covered the history of their people. These plates give a brief spiritual history that, by divine design, compensates for the loss of the beginning portion of Mormon’s record (which was recorded on the 116 pages that were lost by Martin Harris).
Book of Mormon Central, "Why Do the Authors on the Small Plates Follow a Pattern? (Jacob 7:27)," KnoWhy 74 (April 8, 2016).
John W. Welch, "The Father’s Command to Keep Records in the Small Plates of Nephi," FARMS Preliminary Report (September 1984), 1–12.