John is called the Apostle of Love. He wrote John’s gospel deliberately to persuade those who were not believers that they might have life by believing that Jesus is the Christ, the Son of God. This letter was written to believers that they might go on believing with assurance of eternal life.
There are many memorable statements in John’s first epistle. “If we confess our sins, He is faithful and just to forgive us our sins and cleanse us from all unrighteousness.” This is the sequel to John’s Gospel. He wrote so that we might have life through believing that Jesus is the promised Saviour, the Son of God. He wrote this so that our faith in Him would continue, and that we would therefore continue as believers from first to last.