What does 2 John 1:11 mean?

This verse concludes the main body of the letter and John's warnings against false teachers in verses 7–11. John's comment is both direct and powerful. A person who shows hospitality to false teachers "takes part," or "shares," in that sin. In the context of this culture, John has in mind a person who accepts a false teacher into his or her home. This does not mean in a modern, literal sense that a believer cannot say, "hello" or "good morning" to a false teacher. The idea is to avoid anything that even slightly supports a false teacher's work.

John's desire was for believers to walk "in the truth" (2 John 1:4), not to share in wicked work or evil. This means more than simply not doing evil ourselves. As believers, we are also called on to avoid supporting those who teach some other, false gospel (Galatians 1:8). Being polite and loving does necessarily mean advocating or defending. We are not to confuse civility with promoting those who preach a dangerous and phony message.