If the people repent and “come unto me”, they would have eternal life. The voice then declares who he is: “Jesus Christ, the son of God.” That declaration is further qualified by discussing the relationship between Jesus Christ and the Father.
It is easy for modern readers to see these verses in the light of all of the discussions about the nature of the Godhead. That would be anachronous for the Nephites. The Nephites had believed that Jehovah was their God, and that Jehovah would descend to the earth to become the mortal Messiah.
It is in that context that we should see this declaration. The destructions were predicted to accompany the death of the Messiah. This voice identifies himself as the same as the mortal Messiah whose death was witnessed with the destructions and darkness. The title “son of God,” in Nephite terms, meant God while on the earth. Jesus is declaring first that he is the predicted Messiah, who had died. He is also clearly back in the heavens, and in the heavens, the Nephites had called him Jehovah, or God, or the Father.
Modern readers understand the difference between God the Father and Jehovah, his son. That reality may have been known among the Nephites, just as it was at one time among the Hebrews. However, the clear understanding of the division of the two may not have been clearly understood until Christ was among them, and still speaking to his Father. At that time, the meaning of being “with the Father” would be clarified.
The list of titles in verse 15 recalls Samuel’s prophecy that this very being would come: “And also that ye might know of the coming of Jesus Christ, the Son of God, the Father of heaven and of earth, the Creator of all things from the beginning; and that ye might know of the signs of his coming, to the intent that ye might believe on his name” (Helaman 14:12).