What does the Bible say about the communion of saints?

The Bible teaches that the communion of saints, as articulated in Psalm 133, is a critical aspect of Christian life. It highlights the beauty and necessity of unity among believers, describing it as 'good and pleasant' for brethren to dwell together. This is not merely a call for physical gathering, but a profound spiritual unity that reflects the fellowship and love within the body of Christ. The Holy Catholic Church exists both as the eternal fellowship of believers and in every local congregation, signifying the real and visible expression of this divine unity.