2 John

This epistle, along with 3 John, were essentially brief personal letters to believers whom John expected to visit soon. These two small epistles, under the guidance of the Holy Spirit, were retained and essentially rescued from oblivion most likely by being attached to a copy of 1 John in the church (or churches) where they had been received.

This book is also referred to as a "Caution Against False Teachers"—written by the last surviving companion of Jesus at the time.