Q 92 What did God at first reveal unto man as the rule of his obedience?

A. The rule of obedience revealed to Adam in the estate of innocence, and to all mankind in him, besides a special command not to eat of the fruit of the tree knowledge of good and evil, was the moral law.[398]

[398] Genesis 1:26-27. And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth. So God created man in his own image, in the image of God created he him; male and female created he them.

Romans 2:14-15. For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves: Which show the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another;)

Romans 10:5. For Moses describeth the righteousness which is of the law, That the man which doeth those things shall live by them.

Genesis 2:17. But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.