III John 5-8 — “We therefore ought to receive such, that we might be fellowhelpers to the truth.” In this section of the letter, John commends Gaius for showing hospitality to some missionaries who had come through his town on their travels. When they reported back to their sending church, they had testified of the love Gaius had shown them, and John wanted him to continue doing so.
This part of the epistle ends with a general exhortation. All Christians are obliged to support those who’ve devoted their life to Gospel ministry.