110. Gn. adu. Man. 2.21.32; Hill, Genesis, 93; CSEL 91.155.
76 Made to be Godly states of being, God and nothing, they must freely choose to fulfill their self-giving natures by turning to God.
However, having turned away, sinful humanity has chosen mortality over God. Augustine sees this aversion represented in the "garments of skin" Adam and Eve used to obscure themselves before God and before one another as found at Genesis 3:21. Their transparent purity had been sullied by sin, their divine image distorted. In these symbols of mortality, Augustine sees a new and unintended posture of the human person which directly opposes what God originally willed for us, namely, directing our lives toward his perfect image.
After the Fall, Adam and Eve experienced a spiritual death and were condemned to live without the unsullied blessedness they forfeited. They still possessed the divine image but without the clarity that first shone forth, having exchanged immortality for corruption and a certain natural glory for a new depraved condition. In his commentaries on Genesis, Augustine employs the tunicae pellicae to signify the moribund effects of sin: God's condemnation and human mortality. They symbolize the new break in the relationship between the human and the divine as well as the new situation men and women would have to face in a fallen world.
These "coats of skin" represent God's punishment for Adam and Eve's attempt to deceive him. Upon sinning they attempt to cover their newly-recognized nakedness with aprons made out of fig leaves but it was God who made them tunics from the skin of dead animals. Whereas they thought they could live in such a condition of deceit, God acted so as to turn their hearts back to him: "They themselves, you see, had made aprons out of figleaves for themselves, and God made them tunics of skin; that is, they set their hearts on the pleasures of lying after turning their backs on the face of Truth, and God changed their bodies into this mortal flesh, in which lying hearts are concealed."110
110. Gn. adu. Man. 2.21.32; Hill, Genesis, 93; CSEL 91.155.