Death is a part of the plan of God (v. 27). Following death, all men will be judged. As Paul taught, “we must all appear before the judgment seat of Christ” (2 Corinthians 5:10). So that mankind would not be ignorant of the plan of redemption, angels were sent to teach them (Alma 12:28–29). The angels who caused men to behold the glory of God may have brought them to a knowledge of the glory that it was possible for them to attain. Another possible meaning could be that angels in Alma’s day could only appear in glory since they were spirit beings and had no bodies, and thus those to whom angels appeared would see them in glory. The Prophet Joseph Smith taught: “Spirits can only be revealed in flaming fire and glory. Angels have advanced further, their light and glory being tabernacled; and hence they appear in bodily shape” (TPJS, 325). Probably both interpretations are correct. Knowledge was given them “according to their faith and repentance and their holy works” (v. 30). Some were able to see more and learn more of the glory of God than others.
The first commandment given to Adam, not to partake of the fruit of the tree of knowledge of good and evil (see Moses 3:17), was a temporal commandment. Ingesting the fruit caused a change in the physical body and was a transgression not a sin (see 1 Timothy 2:14). After partaking of the fruit, they became “as Gods, knowing good from evil” (Alma 12:31, see also Moses 5:10–11, Articles of Faith 1:2). With choices before them, they were taught the plan of redemption and the consequences of evil. The second death is to be cast out of the presence of God after having been brought back through the resurrection of Christ (see Helaman 14:17–18). Justice would then preempt the power of the redemption because God is a just God as well as a merciful God (Alma 12:32). Mercy cannot rob justice (see Alma 42:23–25). On the other hand, through repentance and yielding one’s heart to God, the mercy of the Only Begotten Son will bring about a remission of sins and a place in the rest of God (Alma 12:34–35), which is the fullness of his glory (see D&C 84:24).