"It's worth noting, as many have, that the authors of the Heidelberg Catechism included their expostion of the law in the gratitude section and not the guilt section. This choice reflects the widespread Reformation belief in the so-called third use of the law. The law is given (1) to restrain wickedness and (2) to show us our guilt and lead us to Christ. But, according to Calvin, the "third and principal use" of the law is as an instrument to learn God's will. The law doesn't just show us our sin so we might be drawn to Christ; it shows us how to live as those who belong to Christ." Kevin DeYoung. The Good News We Almost Forgot. 163.

Question 92: What does the Lord say in His law?

Answer: [The Catechism quotes from Exodus 20:1-17, reciting the giving of the Ten Commandments]

Question 93: How are these commandments divided?

Answer: Into two tables. The first has four commandments, teaching us what our relation to God should be. The second has six commandments, teaching us what we owe our neighbor.

Question 94: What does the Lord require in the First Commandment?

Answer: That I avoid and shun all idolatry, magic, superstitious rites, and prayer to saints or to other creatures. That I sincerely acknowledge the only true God, trust Him alone, look to Him for every good thing humbly and patiently, love Him, fear Him, and honor Him with all my heart. In short, that I give up anything rather than go against His will in any way. 

Question 95: What is idolatry?

Answer: Idolatry is having or inventing something in which one trusts in place of or alongside of the only true God, who has revealed Himself in His Word.