Jacob had just declared, in verse 11, that the way to reconcile ourselves to our God is through the Messiah’s atonement. That atonement is over five hundred years away from being effected. The Nephites know of the six hundred-year prophecy, that the atoning Messiah would come to earth in six hundred years from the time Lehi’s family left Jerusalem. That means they understood that the act of the atonement was in the far, and perhaps unimaginable, future. For this reason, Jacob declares “marvel not that I tell you these things.” Jacob understands that while the act of atonement is in the future, the benefit of that future act applied to them based on the divine promise that it would occur.
Therefore, Jacob speaks of prophesy as “things as they really are, and of things as they really will be; wherefore, these things are manifested unto us plainly, for the salvation of our souls.” When a true prophecy is made, it may speak of things that will be, but in the case of the atonement, it also describes things as they really are. Humankind was capable of salvation before the atonement occurred. Repentance and forgiveness of sins were possible in the lives of those to whom Jacob spoke, even though the atoning act that allowed for repentance and forgiveness of sins had not yet occurred.
In verse 14, Jacob returns to a theme that must have still been present in the minds of those who had left Jerusalem. The Jews, meaning the house of Israel in the Old World, had rejected the prophets. They had lost this important understanding of the atoning mission of the Messiah. Jacob would have been sensitive to the state of the Old Word because he was born there. He was born in the wilderness, but certainly understood that where he was born was a result of Jews who had rejected a specific prophet.