The following is from thewestminsterstandard.org:
Q. 11. What are God’s works of providence?
Q. 12. What special act of providence did God exercise toward man in the estate wherein he was created?
A. When God had created man, he entered into a covenant of life with him, upon condition of perfect obedience; forbidding him to eat of the tree of the knowledge of good and evil, upon the pain of death.
Q. 13. Did our first parents continue in the estate wherein they were created?
A. Our first parents, being left to the freedom of their own will, fell from the estate wherein they were created, by sinning against God.
Q. 14. What is sin?
A. Sin is any want of conformity unto, or transgression of, the law of God.
Q. 15. What was the sin whereby our first parents fell from the estate wherein they were created?
A. The sin whereby our first parents fell from the estate wherein they were created, was their eating the forbidden fruit.
Recommended sermon: The Westminster Assembly, by Dr. Sinclair B. Ferguson