# Beloved, let us love

"You people whom I love, let us love" 

# let us love one another

"believers are to love other believers"

# and everyone who loves is born from God and knows God

"and because those who love their fellow believers have become God's children and know him"

# for love is from God

"because God causes us to love each other"

# born from God

Here this means someone has a relationship to God like a child to his father.