The Prophets write scriptures for our own benefite

“For we labor diligently to write, to persuade our children, and also our brethren, to believe in Christ, and to be reconciled to God; for we know that it is by grace that we are saved, after all we can do. …“And we talk of Christ, we rejoice in Christ, we preach of Christ, we prophesy of Christ, and we write according to our prophecies, that our children may know to what source they may look for a remission of their sins” (2 Nephi 25:23, 26).

The Atonment of Jesus Christ

The Atonement was the foreordained but voluntary act of the Only Begotten Son of God in which He offered His life and spiritual anguish as a redeeming ransom for the effect of the Fall of Adam upon all mankind and for the personal sins of all who repent.
http://jesuschrist.lds.org/SonOfGod/eng/his-life-and-teachings/articles/the-atonement-of-jesus-christ