…the epistle endures. This should come as no surprise to Christians. While we are often described as a people of the book, an important chunk of that book is a collection of letters. Indeed, Christianity is unique in ascribing divine authority to human correspondence. While the form may vary, there is genius and power unique to the epistle. – James K.A. Smith.
There is divine authority in the correspondence between the children of God. Little children, fathers, and young men, as John says, have the word of life in their midst when their words are written in love; when they keep His word, then the love of God is perfected in them. It is humbling to be in the midst of people who love their brothers and abide in the light.
“That which was from the beginning, which we have heard, which we have seen with our eyes, which we looked upon and have touched with our hands, concerning the word of life— the life was made manifest, and we have seen it, and testify to it and proclaim to you the eternal life, which was with the Father and was made manifest to us— that which we have seen and heard we proclaim also to you, so that you too may have fellowship with us; and indeed our fellowship is with the Father and with his Son Jesus Christ. And we are writing these things so that our joy may be complete."
(1 John 1:1-4 ESV)