"They had marked themselves"
In Alma 3:4, Mormon talks about how the Amlicites marked their forehead with a red mark. They did this to distinguish themselves from the Nephites. This marking can be compared to us today. We take upon ourselves markings to distinguish ourselves from others. When we put a uniform or a jersey on, we demonstrate which side we are for. Taking marks upon us is a serious decision. As missionaries, we wear a white shirt, tie, a nice pair of pants and a nametag. We are showing the rest of the world who we are. In the temple, we receive our garments. We are taking marks upon ourselves by using our garments. We show God that we are on His side.
Marks may not always be tangible or physical marks. Our actions are marks on us as well. If we decide to go to an R-rated movie or listen to degrading music, use a bad word or even eat or drink poisonous substances, we mark ourselves. We can mark ourselves by the way we dress, speak, eat and by how we are entertained.
James counsels us to "visit the fatherless and widows in their affliction, and to keep [ourselves] unspotted from (the vices of) the world. (James 1:27)
We are also taught in the Doctrine and Covenants that to keep ourselves unspotted from the world, we should "go to the house of prayer and offer up [our] sacraments" on the Lord's day … in other words, we must keep the Sabbath day holy. (D&C 59:9)
Our Actions Define Us
Not until fairly recently have I heard people call the Book of Mormon racist. At first, I did not know why people would call the Book of Mormon racist, but then it dawned on me. Some people believe that since God put a curse on the Lamanites because they did not believe in keeping the commandments, they think the Book of Mormon is racist. Or better said, these people think that the authors of the Book of Mormon are racists, who use the name of God to establish racism. I don’t believe this garbage.
The curse was just a method to separate the people of God from the people who didn’t want to keep the commandments (see Alma 3:6). There was no commandment that stated that anyone who had a curse could not become a saint. In fact, verse 11 says that a Nephite (by definition) is anyone who did not believe in the traditions of the Lamanites, but rather believed in the records that Lehi brought out of Jerusalem and who believed the commandments and in keeping the commandments. We will later see that Ammon and his brethren converted many Lamanites and these Lamanites become strong members of the church, despite their “curse.”
The common trait among all those who did not keep the commandments was that they brought it upon themselves (Alma 3:19). The Amlicites marked their selves and thus were distinguished from the Nephites.
In today’s terms, people distinguish themselves from the saints of God. Some distinguishing marks are: sexually transmitted diseases, the way people dress, the language they use, the company they keep and the lifestyle they live. Just from these distinguishing traits, people separate them selves from the members of the Church. Similarly, just as Lamanites could become converted to the Gospel and have the curse lifted, so can people today repent of their evil ways and becomes sons of God.
A boomerang is not only a neat word, but it is a device that when thrown, travels a distance and then returns to its point of origin. In a gospel context, it means that if you "do good" you will "receive good." If you "do bad", then you will "receive bad." Those are very simplified terms, but the idea is the same as "you sow what you reap."
Alma 41:14-15 does an excellent job in summing up the Boomerang Effect in terms of the gospel.
"Therefore, my son, see that you are merciful unto your brethren; deal justly, judge righteously, and do good continually; and if ye do all these things then shall ye receive your reward; yea, ye shall have mercy restored unto you again; ye shall have justice restored unto you again; ye shall have a righteous judgment restored unto you again; and ye shall have good rewarded unto you again.
"For that which ye do send out shall return unto you again, and be restored; therefore, the word restoration more fully condemneth the sinner, and justifieth him not at all."
King Benjamin taught this same doctrine in Mosiah 2:33, 37. We also read of this idea in Alma 3:26-27 and Alma 5:41-42.