Shared ground
John 20:8–10 presents a tight sequence: the second disciple finally enters the tomb, sees the scene inside, and “believes.” Then the narrator adds a clarifying note: at that point “they” still did not know from scripture that Jesus had to rise from the dead. The scene ends quietly, with the disciples going back home.
Explicitly, the text links belief to what was seen in the tomb (v. 8), while also stating that Scripture-based understanding of resurrection was not yet in place (v. 9). That combination makes room for belief that is real but incomplete.
Where interpretation differs (only where needed)
What, exactly, did the disciple “believe”?
Some read the belief in v. 8 as belief that Jesus had been raised. Others read it as belief that Mary’s report was accurate (the body was gone), or that something significant had happened, without a formed conclusion about resurrection.
Who is included in “they” in v. 9?
Some take “they” to mean the two disciples at the tomb. Others think it could be broader (the disciples generally), with the narrator summarizing the group’s state of understanding at that stage.
Which Scripture is meant, and what does “must” mean?
The passage does not name the specific text(s). “Must” (necessity) is often taken as God’s plan being fulfilled, not merely that resurrection was likely or hoped for.
Why the disagreement exists
John reports a belief-response (v. 8) and immediately qualifies understanding (v. 9) without spelling out the content of the belief. The narration is compressed, and key referents are left implicit: the exact object of belief, the scope of “they,” and the exact Scripture(s) in view.
What this passage clearly contributes
The passage distinguishes between (1) responding in belief to eyewitness evidence and (2) grasping how that event fits Scripture’s message about Jesus rising. It also portrays the early resurrection morning as a moment of partial clarity: something has been recognized, but the larger scriptural meaning is not yet understood. The quiet departure in v. 10 underscores that this is an initial turning point rather than a full resolution (John 20:11–18 will carry the narrative forward).