This book/chapter is short and sweet but it carries a big message.
The background to this book is that in the early centuries after Christ, the gospel was taken from place to place by traveling evangelists. People would take these men into their homes and give them a place to stay and provisions for the rest of their journey. Gnostic teachers (which we studied about in 1 John) also relied on this practice as well. 2 John was written to urge discernment by these homes when it came to supporting these travelers.
John opens by calling himself and "elder." This could either be an official title that the disciples used to be called or because he was speaking to a group of younger people. It is not very clear which though. The same goes for the phrase "the chosen lady and her children." This could either be because he was actually speaking to a woman and her children of that the church is the woman and the members her children. Based on the rest of the passage it would seem that the church and its members fits best. In verse 3 he speaks on three very important words Grace, Mercy, and Peace. Grace means having favor and Peace means wholeness(physical, mental, and spiritual). Mercy is a combination of love and pity to which it always seeks the best for its objects.
John was so excited to hear what the members of the church had been doing for those around them. They were following the love commandment that was mentioned previously in 1 John. They were truly acting out on what they were been taught.
John really speaks against the false teachers in these verse. It can be said that he was referring to the Gnostic teachers that he spoke on in 1 John. He is warning the people not to open their doors to them or even give them a greeting. Back then when people invited guest into their homes it was a big gesture. It involved fellowship and acceptance. John doesn't want the people to push aside the teachings of Christ that they have learned in order to accommodate a false teacher.
John seemed to be a very personal man and would rather speak face to face with someone then on paper. This shows me that he had a boldness about him and that he was easily intimidated. In verse 13 he speaks of a "chosen sister" which he probably meant a sister church to the one that they were members of.
* After studying this passage I thought about how many people we have had stay at our home over the years, each with their own stories and testaments. My prayer is that we have never allowed or will allow someone who is going against the teachings of the Lord to come in and corrupt our hearts.