Master, which is the great commandment in the law?. Jesus said unto him, Thou shalt love the Lord thy God with all thy heart,and with all thy soul, and with all thy mind, this is the first and gratest commandment. And the second is like unto it, Thou shalt love thy neighbour as thyself. On these two commandments hang all the law and prophets (Matt.22:36-40)See also Rom.13:8-10
The bible further defines what love of God is and love of neighbor is. Love of God is keeping the first four of the ten commandments. Love of our neighbor is keeping the last six. The new convenent writes those laws into our hearts.