I learned a couple of things while reading 3 Nephi 15: how Jesus fulfilled the Mosaic law; and that the Gentiles were not the ‘other fold’ which Jesus spoke of in Jerusalem.
Jesus fulfilled the Mosaic law, because He was perfect. The Mosaic law was written to delineate sin. To fulfill this law, Jesus did not sin. He was perfect and sinless. Therefore, He became the law, and atoned for us, who do sin often. We should follow His example, so that through His Atonement, we can be forgiven for our transgressions, be guided by the Holy Ghost, and humbly walk the path towards exaltation.
The other, even more remarkable, thing that I learned was that the Gentiles were not the ‘other fold’ which Jesus spoke of in Jerusalem (John 10:16). The Gentiles would not be taught by Jesus, for they were converted by the power of the Holy Ghost (3 Nephi 15:23).