WSC Q.42: What is the sum of the ten commandments?
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 neighbour as ourselves. (Matt. 22:37–40)
WLC Q.122: What is the sum of the six commandments which contain our duty to man?
The sum of the six commandments which contain our duty to man, is, to love our neighbour as ourselves, (Matt. 22:39) and to do to others what we would have them to do to us. (Matt. 7:12)