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 great commandment.
The Lord our God is one Lord: and thou shalt love the Lord thy God with all thine heart, and with all thy soul, and with all thy might. And these words, which I command thee this day, shall be in thine heart: and thou shalt teach them diligently unto thy children, and shalt talk of them when thou sittest in thine house, and when thou walkest by the way, and when thou liest down, and when thou risest up.
Loving God means keeping His commandments and one aspect of this is to love one another:
Beloved, if God so loved us, we ought also to love one another
1 John 3:23