One measure of the new birth is the appearance of the new man. Paul described the process of salvation as obtaining “the mind of Christ” (1 Corinthians 2:16); that is, learning to think as Christ thinks, believe as he believes, feel as he feels, and do as he would do. Peter described the same thing as partaking of “the divine nature” (2 Peter 1:4), meaning that we must acquire the attributes of godliness.
Joseph Smith explained: “The Savior most clearly show[ed] unto us the nature of salvation, and what he proposed unto the human family when he proposed to save them- that he proposed to make them like unto himself, and he was like the Father, the great prototype of all saved beings; and for any portion of the human family to be assimilated into their likeness is to be saved; and to be unlike them is to be destroyed; and on this hinge turns the door of salvation” (Lectures on Faith 7:16).
As a child learns by imitating and emulating parents and those older than himself, so we learn godliness by imitating others who have set an example in righteousness, especially Jesus Christ. Alma appropriately describes this process of becoming Christlike as receiving the image of Christ in our countenances.