N Romans 5:10 we are told that we are reconciled to God by Christ's death, but saved by His life. Here in John 20, there is no room for doubt concerning the claim of John: 3 days after His death, Jesus did come back to life. It's a good thing too. Sadly though, there are many who do not benefit from His resurrection. The fault is not with God though. This account of Christ's victory over death has been given so that people will "believe that Jesus is the Christ, the Son of God; & that believing [they] might have life through His name" (vs. 31).
Mary Magdalene found Christ's tomb open & empty on that first Sunday morning after the crucifixion (vs. 1). So also did Peter & John (vs. 2). Additionally, there were 2 angels who visibly bore witness to the empty tomb (vs. 12). Jesus Himself testified of His own resurrection (vs. 14-18), which is (for obvious reasons) a little more convincing than any other person's account. Then, there were 10 of Jesus' disciples who saw Him alive during the first Sunday evening assembly of the church (vs. 19). Thomas saw Him alive about a week later (vs. 26-28). And, through the eyes of faith, we also have seen Him alive (vs. 29). He is alive & living in us!