The elder says he loves the recipients “in truth,” and he links that love to “the truth that abides in us” (2 John 1:1–2). He later connects truth to “walking according to his commandments” (2 John 1:4–6). He also warns that deceivers deny Jesus Christ coming in the flesh, opposing the truth (2 John 1:7).
In 2 John 1:1–3, the writer calls himself “the elder” and addresses “the elect lady and her children.” He says his love for them is “in truth,” and that this love is shared by all who have come to know the truth. He explains that this shared bond exists because the truth remains among them and will stay with them. These verses function as the letter’s opening greeting and set the terms that the rest of the message will keep returning to: “truth” and “love.” The writer first identifies sender and recipients, then explains why his relationship to them is more than personal affection: it is anchored in a shared “truth” that is.
The opening lines present a relationship held together by two realities: truth (truth) and love. Explicitly, the writer (“the elder”) says he loves the recipients “in truth,” and that this is shared by “all those who know the truth” (verse 1).
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with 2 John 1:1-2, then read the surrounding section so the answer stays connected to the passage's flow.
1The elder, to the elect lady and her children, whom I love in truth; and not I only, but also all those who know the truth;
2for the truth`s sake, which remains in us, and it will be with us forever: