Shorter Catechism
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.1
Larger Catechism
Q 122. What is the sum of the six commandments which contain our duty to man?
A. The sum of the six commandments which contain our duty to man is, to love our neighbor as ourselves,2 and to do to others what we would have them to do to us.3
Matthew 22:37-40
And he said to him, “You shall love the Lord your God with all your heart and with all your soul and with all your mind. This is the great and first commandment. And a second is like it: You shall love your neighbor as yourself. On these two commandments depend all the Law and the Prophets.” (ESV)
Matthew 22:39
And a second is like it: You shall love your neighbor as yourself. (ESV)
Matthew 7:12
“So whatever you wish that others would do to you, do also to them, for this is the Law and the Prophets. (ESV)