Answer: 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 of the knowledge of good and evil, was the moral law.₁

1. Genesis 1:26-27; Romans 2:14-15; Romans 10:5; Genesis 2:17

For further study see:

1. Q40. What did God at first reveal to man for the rule of his obedience?