But since the will of man could turn either way,
God secured this grace that He had given by making it conditional from the first upon two things:
namely, a law and a place.
He set them in His own paradise, and laid upon them a single prohibition.
If they guarded the grace and retained the loveliness of their original innocence,
then the life of paradise should be theirs, without sorrow, pain, or care,
and after it the assurance of immortality in heaven.
But if they went astray and became vile, throwing away their birthright of beauty,
then they would come under the natural law of death and live no longer in paradise,
but, dying outside of it, continue in death and corruption.
This is what Holy Scripture tells us…
“You may freely eat of every tree of the garden;

but of the tree of the knowledge of good and evil you shall not eat,
for in the day that you eat of it you shall die” (Gen 2:16-17).
“You shall die” – not just die only,
but remain in the state of 
death and of corruption.
(St. Athanasius, On the Incarnation)