3 John 1:3
3 John 1:33For I was overjoyed when the brothers came and testified about your devotion to the truth, in which you continue to walk.
Read as commendation of a faithful individual holding to accurate teaching. The phrase "walking in the truth" maps naturally onto Watchtower usage, where being in the Truth means being associated with the organisation and keeping its teachings.
Notice how John speaks about it: the truth you hold, and you go on walking in the truth. It is something a person holds and walks in — a message lived out, not an organisation joined. This is one of the clearest places to make the vocabulary point, because John repeats the word twice in a single sentence and both times it behaves like a message rather than an institution. He does the same at and again a verse later here. Set that beside the New Testament's other uses — Jesus as the truth (), the Spirit of truth (), the word of the truth which is the good news (, ) — and the pattern holds without exception. The point is not to catch anyone out. It is that when "the Truth" becomes the name of a group, the group has quietly moved into the place the New Testament reserves for Christ. Ask gently what a Witness means by the phrase, read two or three of these verses, and leave it there. Compare , , .