Passage
But this happened to fulfill the word that is written in their Law, ‘They hated Me without cause.’
John 15:25 (LSB)
Nearby Context
John 15:23 He who hates Me hates My Father also.
John 15:24 If I had not done among them the works which no one else did, they would not have sin; but now they have both seen and hated Me and My Father as well.
John 15:25 But this happened to fulfill the word that is written in their Law, ‘They hated Me without cause.’
John 15:26 “When the Advocate comes, whom I will send to you from the Father, the Spirit of truth who proceeds from the Father, He will bear witness about Me,
John 15:27 and you will bear witness also, because you have been with Me from the beginning.
Study Lenses
The verse centers on "happened", "fulfill", "word", "written", "hated", "without", and "cause". It is saying that the verse draws attention to "happened" and "fulfill", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 24's "If I had not done among them..." into verse 26's "When the Advocate comes whom I will...", so "happened" and "fulfill" belong inside that flow. In John context, the local focus is the identity of Jesus, new birth, eternal life, and belief and unbelief.
A plain takeaway is to answer the verse's own emphasis on "happened" and "fulfill" with trust shaped by these words, not by a vague optimism outside the passage.