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, all our soul, with all our strength, and with all our mind; and our neighbor as ourselves.

When asked by a lawyer, “Teacher, which is the great commandment in the Law?” Jesus 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 foremost commandment. The second is like it, ‘YOU SHALL LOVE YOUR NEIGHBOR AS YOURSELF.’ On these two commandments depend the whole Law and the Prophets.” (Matthew 22:34-40)

In Romans 13:9, the apostle Paul sites several of the Ten Commandments that show one’s responsibility to others, and he says that all of these commandments are fulfilled in the call to love one’s neighbor as one loves self.