One of the greatest books written in the 20th century regarding how live in the family of faith is Dietrich Bonhoeffer’s, Life Together. The entire book is simply an exposition of the first line of Psalm 133: "Behold, how good and pleasant it is for brothers to dwell together in unity."

Therefore, the Christian needs another Christian who speaks God's Word to him. He needs him again and again when he becomes uncertain and discouraged for by himself he cannot help himself without belying the truth. He needs his brother as a bearer and proclaimer of the divine word of salvation. The Christ in his own heart is weaker than the Christ in the word of his brother. His own heart is certain, his brother’s is sure.