1 John 1:3-4
That which we have seen and heard declare we unto you, that ye also may have fellowship with us: and truly our fellowship is with the Father, and with his Son Jesus Christ. And these things write we unto you, that your joy may be full.
The book of 1st John is an Apostolic Letter written by the Apostle John around 85-95 A.D. probably from Ephesus. Its purpose was to warn about the increasing threat of false teachings and to reassure Christians of their faith and love in Jesus Christ.
It was written to combat false teachings. The Apostle John very clearly writes to give the true tests of a true Christian. He gives several means to measure the reality of one’s conversion experience.
One big test is written in 1 John 1:10, “If we say that we have not sinned, we make him a liar, and his word is not in us.” While this certainly applies to our initial conversion and salvation it also applies to our daily walk with the Lord. How can any human being possibly believe that they are doing everything perfect? None of us are just like Jesus yet. If I feel like I did it perfectly and could not have improved in any aspect in what happened, I am deceived. A Christian once was heard to say, “I don’t have anything to repent for. It is my season of exaltation.” According to the Apostle John’s letter, that cannot be.
John said, “And these things write we unto you, that your joy may be full.” How then is our joy full? This word full is also used in Romans 8:4 and is written as fulfilled, “That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.” So when the righteousness of the law is fulfilled in us our joy is full. The law cannot be fulfilled by what we do because we cannot say that we have no sin in us as we are imperfect human beings. However when we learn to walk after the Spirit, Christ comes and fulfills the law in us. We therefore are filled with the joy of the LORD and His love fills our heart and overflows to all around us.
As it says in John 7:38, “He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water.”