Confucius said: “Virtue never stands alone; it always has neighbors.”
Chapter 1 and Chapter 25 of Book 4 have similar themes: virtuous people attract others like a magnet.
Ziyou said: “In the service of a lord officiousness inevitably brings disgrace; in the company of friends, it brings estrangement.”
Like Chapter 15, Chapter 26 appears to have been shoehorned into Book 4 at a later date. All the other chapters in the book feature an aphorism from Confucius.
You can read the complete translation of Book 4 here.