Q. 39–42, The Moral Law

Q. 39. What is the duty which God requireth of man?
A. The duty which God requireth of man is obedience to his revealed will.

Q. 40. What did God at first reveal to man for the rule of his obedience?
A. The rule which God at first revealed to man for his obedience was the moral law.

Q. 41. Where is the moral law summarily comprehended?
A. The moral law is summarily comprehended in the ten commandments.

Q. 42. What is the sum of the ten commandments?
A. The sum of the ten commandments is to love the Lord our God with all our heart, with all our soul, with all our strength, and with all our mind; and our neighbor as ourselves.

Proof Texts

Q. 39: Deut. 29:29; Mic. 6:8; 1 John 5:2–3. Q. 40: Rom. 2:14–15; Rom. 10:5. Q. 41: Deut. 4:13; Matt. 19:17–19. Q. 42: Matt. 22:37–40.

Harmony with Westminster Standards

WCF 19.1-2; WLC 91-98, 102, 122.

Additional Resources

Sermons by James Cassidy on the Westminster Shorter Catechism

Questions 39-42: “Man’s Duty”


J. Aspinwall Hodge, The System of Theology Contained in the Westminster Shorter Catechism: Opened and Explained (New York: A. C. Armstrong and Son, 1888), 81-84.

Thomas Vincent, The Shorter Catechism of the Westminster Assembly Explained and Proved From Scripture (Edinburgh: The Banner of Truth Trust, 1998), 109-115.

Johannes G. Vos, The Westminster Larger Catechism: A Commentary, ed. G. I. Williamson (Phillipsburg, NJ: P & R, 2002), 221-241.

Thomas Watson, The Ten Commandments (Edinburgh: The Banner of Truth Trust, 1970), 1-12

Alexander Whyte, A Commentary on the Shorter Catechism (Edinburgh: T. & T. Clark, 1977), 100-106;

G. I. Williamson, The Westminster Shorter Catechism for Study Classes, 2nd ed (Phillipsburg, NJ: P & R, 2003), 181-186.

On Key


Van Til’s Trinitarian Theology

Designed to equip the student to engage critically central issues in trinitarian theology, this course will focus on the architectonic significance of the Trinity both