First John 5:7 :

"For there are three that bear record in heaven,
the Father, the Word, and the Holy Ghost:
and these three are one."

Links To Articles On First John 5:7

And These Three Are One (1 John 5:7-8) By Jesse M. Boyd

1 John 5:7-8: Is It Inspired Scripture? By John Henry

The Johannine Comma By Floyd Jones