Irenaeus: Demonstration of the Apostolic Preaching

15. But, lest man should conceive thoughts too high, and be exalted and uplifted, as though he had no lord, because of the authority and freedom granted to him, and so should transgress against his maker God, overpassing his measure, and entertain selfish imaginings of pride in opposition to God; a law was given to him by God, in order that he might perceive that he had as lord the Lord of all. And He set him certain limitations, so that, if he should keep the commandment of God, he should ever remain such as he was, that is to say, immortal; but, if he should not keep it, he should become mortal and be dissolved to earth from whence his formation had been taken. Now the commandment was this: Of every tree that is in the Paradise thou shalt freely eat; but of that tree alone from which is the knowledge of good and evil, of it thou shalt not eat; for in the day thou eatest, thou shalt surely die.