One of the important principles of the gospel was an understanding of one’s relationship with Jehovah. In particular, sin removed one from God’s presence. In the Nephite teaching, this became a personal, rather than communal, sin, and depended upon the coming Messiah’s atoning sacrifice to cleanse. Even though the act was in the future, the benefit of the promised act was available to all who believed. Thus, Jehovah “hath granted unto us that we might repent of these things.”
Of what did they repent? What did they consider to be so serious? Anti-Nephi-Lehi lays out the crucial sins: “the many murders which we have committed.” In verse 10 he reiterates that: “He hath forgiven us of those our many sins and murders which we have committed.”
The importance of repenting of the many murders becomes the reason that they should no more take up weapons of war in the next verses.