City of God

If any one finds a difficulty in understanding why other sins do not alter human nature as it was altered by the transgression of those first human beings, so that on account of it this nature is subject to the great corruption we feel and see, and to death, and is distracted and tossed with so many furious and contending emotions, and is certainly far different from what it was before sin, even though it were then lodged in an animal body—if, I say, any one is moved by this, he ought not to think that that sin was a small and light one because it was committed about food, and that not bad nor noxious, except because it was forbidden; for in that spot of singular felicity God could not have created and planted any evil thing.

But by the precept He gave, God commended obedience, which is, in a sort, the mother and guardian of all the virtues in the reasonable creature, which was so created that submission is advantageous to it, while the fulfillment of its own will in preference to the Creator's is destruction. And as this commandment enjoining abstinence from one kind of food in the midst of great abundance of other kinds was so easy to keep—so light a burden to the memory,— and, above all, found no resistance to its observance in lust, which only afterwards sprung up as the penal consequence of sin, the iniquity of violating it was all the greater in proportion to the ease with which it might have been kept.