1 John in Wikipedia

The First Epistle of John, usually referred to simply as First John and often written 1 John, is a book of the New Testament. This fourth catholic or "general" epistle is attributed to John the Evangelist, traditionally thought to be the author of the Gospel of John and the other two Epistles of John. This Epistle was written in Ephesus between the years 100-110.[1] The work was written to counter the heresies that Jesus did not come "in the flesh," but only as a spirit. It also defined how Christians are to discern true teachers: by their ethics, their proclamation of Jesus in the flesh, and by their love.[1]...

Link: https://en.wikipedia.org/wiki/1_John