The eighteenth of the Epistles, and the twenty-third book in the New Testament, is I John. It is the first of three letters written by the apostle to be found in the Bible.
The letter was written around 90 AD, some 50 or 60 years since Jesus' crucifixion, and John was now an old man. He was probably the only one of Jesus' 12 disciples still alive at this time, and so his words would have been well respected amongst Christians.
Like II Peter, written some 20 years before, I John is concerned with false teachers who have entered the church. John tells his readers what it means to have fellowship with God, and he warns them about teachers who reject Christ's birth.
I John 4:16-18
"And we have known and believed the love that God hath to us. God is love; and he that dwelleth in love dwelleth in God, and God in him. Herein is our love made perfect, that we may have boldness in the day of judgment: because as he is, so are we in this world. There is no fear in love; but perfect love casteth out fear: because fear hath torment. He that feareth is not made perfect in love"