John had spent time with Jesus and it shows in all he wrote: the gospel of John and the 3 short letters of 1st, 2nd and 3rd John. The reoccurring themes in his writing are truth and love, two things that Christ stood for. Having walked with Christ, he picked on things that resonated with him and that were key to the Saviour. The first of these is love 1 John 2:28-3:2 and 1 John 3:11-24.