1 John 1:3
We proclaim to you what we have seen and heard, so that you also may have fellowship with us. And our fellowship is with the Father and with his Son, Jesus Christ.
In this book, John's teaching was about shared fellowship. The idea of fellowship, from the Greek koinōnia, was an important concept in the New Testament (Acts 2:42).
In 1 John 1:3, John gives the importance of fellowship with each other. And, he reminds us that we also have fellowship with both Christ and God the Father.
This reflects the Great Commandment, found in Matthew 22:37–40, to love God and love your neighbor as yourself. As we fellowship and share with one another, we strengthen our walk with the Lord.
A right relationship with God is seen as essential to right relationships with people.