John 20:8 New English Translation

⁸Then the other disciple, who had reached the tomb first, came in, and he saw and believed.^[a]

John 20:8 sn What was it that the beloved disciple believed (since v. 7 describes what he saw)? Sometimes it is suggested that what he believed was Mary Magdalene’s report that the body had been stolen. But this could hardly be the case; the way the entire scene is narrated such a trivial conclusion would amount to an anticlimax. It is true that the use of the plural “they” in the following verse applied to both Peter and the beloved disciple, and this appears to be a difficulty if one understands that the beloved disciple believed at this point in Jesus’ resurrection. But it is not an insuperable difficulty, since all it affirms is that at this time neither Peter nor the beloved disciple had understood the scripture concerning the resurrection. Thus it appears the author intends his reader to understand that when the beloved disciple entered the tomb after Peter and saw the state of the graveclothes, he believed in the resurrection, i.e., that Jesus had risen from the dead.

New English Translation (NET)