The purpose of Christ’s example is not to show us a way to believe, but a way to be. Nephi makes it clear that we are to “do the things which I have told you I have seen that your Lord and your Redeemer should do.” Nephi had earlier explained that we are saved by grace, after all we can do (2 Nephi 25:23). Grace enables, but doing exalts.
The basic doctrine of Christ is defined in verse 18. We have before us a “strait and narrow path which leads to eternal life.” We enter in by the gate of baptism, but must still do the will, and the commandments of the Father. We receive the Holy Ghost to assist in that process and which witnesses to the truth of the path we are to walk, and the commandments that refine us as we walk. Doing so fulfills the promise, which is eternal life.