First Epistle of John

The First Epistle of John is a sermon attributed to John important in that it establishes that Jesus is of the flesh instead of of the spirit, two contentious positions in the first and second Century C.E.

The works of "John" can be historically positioned at a time when there were at least 5 major Churches, including the Church of Paul (which of course would later solidify into the Orthodox and Roman Catholic churches), and the Essenes who were for the most part Gnostic in their understanding of God and Jesus.

John's comma
A whole lotta fuss for a single line, 1 John 5:7-8. How often are wars fought over less than 10 words? 1 John, in some translations, explicitly references the so called "Holy Trinity". However, this phrase does not appear in the earliest Greek works, likely appearing in the Middle Ages. Ah, Bible translation fun.

5:7 "For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one. 5:8 And there are three that bear witness in earth, the Spirit, and the water, and the blood: and these three agree in one."