Verse 20 has an interesting parallelism. The phrases “steadfastness in Christ” and “endure to the end” are the same concept. They are intentional synonyms, and highlight that each clause beginning with “wherefore” is part of the same idea. The first “wherefore” clause contains the command: “ye must press forward.” The second “wherefore” clause contains the conditional promise: “if ye shall press forward.”
The key to the process is that we understand that it is a process. Beginning the process by simply entering the path is insufficient. If we enter and stop progressing, we do not achieve the end. For that reason, “ye must press forward with a steadfastness in Christ, having a perfect brightness of hope, and a love of God and of all men.” That pressing forward with steadfastness is a parallel to enduring to the end.
Nephi concludes this discourse of the import of the atoning Messiah’s mission by noting that “there is none other way nor name given under heaven whereby man can be saved in the kingdom of God.” Modern Latter-day Saints understand that more is meant by being saved in the kingdom of God than simply having a remission of sins. The goal is eternal life. Nephi taught the doctrine of Christ, and taught that it is the only way to achieve that ultimate goal of eternal life.
Nephi closes by leaving his testimony with the declarative Amen.