The Second Epistle of John is a book of the New Testament. It is the shortest book in the entire Bible: it consists of only thirteen verses.

It is a letter addressed to "the elect lady" (Ἐκκλεκτῇ) and closes with the words "The children of your elect sister greet you" (2 John 13). Of the thirteen verses that compose this epistle, seven are contained in the first of John. The person to whom the letter is addressed is commended for his piety and warned against false teachers.

(From Italian Wikipedia)