Up to this point, Jesus has quoted and expounded scriptures that were known in writing among the Nephites. For example, the priests of Noah had quoted Alma 52 when they challenged Abinadi, and he quoted Isaiah 53 in his reply to them. And since they had Isaiah 53, they probably already had Isaiah 54 too; and Micah was a very early Israelite prophet whose writings also could have been known to the Nephites as well, although we don’t know for sure about that.
But 3 Nephi 23:6 says that after Jesus “had expounded all the scriptures unto them which they had [previously] received,” he discussed “other scriptures … that ye have not.” Accordingly, in these chapters, Jesus added one missing point to the Nephite record of the prophecy of Samuel the Lamanite, and then he quoted to them Malachi 3–4, in 3 Nephi 24–25, which they apparently did not already have.