The Father and the Son
Christ is referred to as the Father and the Son, even though he is a separate being from God the Father. Abinadi explains why Christ is the Father.
First, Christ is referred to the Father because he possesses the same attributes as His father. As Mosiah 15:3 says, "The Father, because he was conceived by the power of God." Just as I inherited brown eyes from my father, Christ inherited the power of God. In D&C 93:4, Christ further explains, "The Father because he gave me of his fullness."
Christ is referred to as the Father because of his function in creating heaven and earth. Helaman 14:12 explains that Christ is the "Creator of all things from the beginning."
Lastly, Christ is the Father because He is the father of our reborn-souls. The people under the reign of King Benjamin were given a new name because of their change in hearts (see Mosiah 5:7).
Abinadi also explains why he is referred to as the Son.
"Because he dwelleth in the flesh he shall be called the Son of God." (Mosiah 15:2)
The Workings of the Atonement
For a very long time, I had a difficult time understanding how the atonement worked. How was it possible that Christ could take upon himself my sins and the sins of every other human being? My mind simply could not grasp the concept.
There are two scriptures in the Book of Mormon that have helped me understand the atonement more than any other passage of scripture. Mosiah 15:9 is one of the scriptures.
"Having the bowels of mercy; being filled with compassion towards the children of men; standing betwixt them and justice; having broken the bands of death, taken upon himself their iniquity and their transgressions, having redeemed them, and satisfied the demands of justice."
The first part of that scripture … "having the bowels of mercy; being filled with compassion towards the children of men; standing betwixt them and justice" begins to enlighten us. In my mind, I view justice as being more stalwart and steadfast than mercy. NO MATTER WHAT, justice will be fulfilled. Mercy, on the other hand, is powerful, but normally not powerful enough to fulfill the demands of justice. God's infinite love for His children was proven when He sent His son to die for all His children. Our Father loves us enough to sacrifice His son and Christ loves His father and us so much, that he'd fulfill the demands of justice for us all … he would live a sinless life and be tempted and not yield to temptation and suffer mocking and scourging and pain and sickness. He showed so much mercy for us, that mercy overpowered justice.
The other scripture is Alma 34:15-16 which states, "And thus he shall bring salvation to all those who shall believe on his name; this being the intent of this last sacrifice, to bring about the bowels of mercy, which overpowereth justice, and bringeth about means unto men that they may have faith unto repentance.
"And thus mercy can satisfy the demands of justice, and encircles them in the arms of safety, while he that exercises no faith unto repentance is exposed to the whole law of the demands of justice; therefore only unto him that has faith unto repentance is brought about the great and eternal plan of redemption."
Elder Scott, in the October 2006 General Conference said of the atonement, "I believe that no matter how diligently you try, you cannot with your human mind fully comprehend the eternal significance of the Atonement nor fully understand how it was accomplished. We can only appreciate in the smallest measure what it cost the Savior in pain, anguish, and suffering or how difficult it was for our Father in Heaven to see His Son experience the incomparable challenge of His Atonement. Even so, you should conscientiously study the Atonement to understand it as well as you can. You can learn what is needful to live His commandments, to enjoy peace and happiness in mortal life. You can qualify, with obedient family members, to live with Him and your Father in Heaven forever." (Richard G. Scott, “The Atonement Can Secure Your Peace and Happiness,” Ensign, Nov 2006, 40–42)
The Seed of Christ
The seed of Christ are those who have heard and hearkened unto the words of the prophets which have prophesied of the coming of Christ. The seed of Christ are all those who look forward to His coming because they look forward to a remission of their sins. The prophets themselves who have published peace are the seed of Christ too. All the prophet who have testified of Christ, who now testify of Christ and who will testify of Christ are also the seed of Christ.
The First Resurrection
Abinadi explains in verse 22 that the first resurrection is the resurrection "of all the prophets, and all those that have believed in their words, or all those that have kept the commandments of God."
D&C 76:50-70 further explains those who will take part in the first resurrection or the resurrection of the just.
Salvation by Grace and Works
Perhaps the biggest debate between mainstream Christianity and "Mormonism" is that of salvation by grace or works.
Abinadi teaches that both are required. If it were not for the grace of God (sending His son to die for our sins), we would have not been redeemed (Mosiah 15:19). If we rebel against God and die in our sins, we will not be redeemed and take part in the first resurrection (Mosiah 15:26) for God "cannot deny justice when it has its claim" (Mosiah 15:27).
In order to be "saved", first Christ had to accomplish his mission; for without Christ accomplishing his mission, there would be no point of salvation. Secondly, how can a person dwell in the presence of God if he is not clean? He must be clean; he must be righteous. I cannot see how a person who claims belief in Christ or says a prayer saying he believes in Christ and then proceeds to live a life of debauchery and then dies can consequently be "saved" and live in the presence of God.
The LDS doctrine on grace and works can easily be found on the LDS.org website. For convenience, here are a few articles that further explain the LDS doctrine on grace and works:
M. Russell Ballard, “Building Bridges of Understanding,” Ensign, Jun 1998, 62
Gerald N. Lund, “Salvation: By Grace or by Works?,” Ensign, Apr 1981, 17
Dallin H. Oaks, “Have You Been Saved?,” Ensign, May 1998, 55
“I Have a Question,” Ensign, Jul 1989, 59–61
James E. Faust, “The Atonement: Our Greatest Hope,” Ensign, Nov 2001, 18