John 20:8

Encouraged by Peter’s boldness John also proceeded into the tomb. There he saw (Gr. eiden, perceived intelligently) this evidence and believed what it implied. He believed that Jesus was alive. In this chapter, John carefully recorded that disciples who saw the resurrected Jesus believed on Him (cf. John 20:16; John 20:20; John 20:25; John 20:29). The writer did not explain what John believed here, but in the context of this chapter it seems clear that he believed that Jesus was alive (cf. John 2:22; John 11:25; John 16:22). The evidence of Jesus’ resurrection convinced John even before he met the risen Jesus. Disciples since John can believe in Him because of this evidence too even though we have not yet seen the risen Jesus (cf. John 20:29; 1 John 1:1-4).

The writer did not say that Peter also believed. This omission does not necessarily mean that Peter failed to believe. The writer was simply confessing his own belief, not contrasting it with Peter’s reaction. Nevertheless John seems to have understood the significance of the empty tomb and the orderly grave clothes better than Peter did (cf. Luke 24:12). He evidently did not confess his belief to others then (cf. John 20:10-18).

Jesus had passed through the grave clothes and through the rocky tomb. The angel opened the tomb to admit the disciples, not to release Jesus (Matthew 28:2).