What does Mark 16:13 mean?

The witnesses to the resurrection are listed in an increasing level of experience and legal reliability. First, women tell the disciples that the tomb is empty and an angel told them Jesus is alive (Matthew 28:1–8). In most cases, women were not allowed to give testimony legally, so next is Peter and John who confirm Jesus is not in the tomb (John 20:3–8; Luke 24:12). Still the disciples don't understand (John 20:9). Next, Jesus appears to Mary Magdalene in person (John 20:11–18). Again, as a woman she is not believed. So Jesus appears to two men, Cleopas and another follower (Luke 24:13–35). According to Luke 24:34 He also appeared to Peter.

Mark 16:9–20 is not found in the oldest, most reliable manuscripts, but all but a very few phrases are corroborated in the other Gospels or the book of Acts. Luke 24:33–35 affirms that Cleopas and his friend returned to Jerusalem and told the disciples they had seen Jesus. That the disciples didn't believe them is not specifically stated in any other text. When the two men return from Emmaus, they find the Eleven and others gathered, saying, "The Lord has risen indeed, and has appeared to Simon!" (Luke 24:34). That being said, it seems there was still some level of disbelief, as inferred from their reactions when Jesus reveals Himself to the group.

As Cleopas and his friend are telling the room full of Christ-followers, Jesus, Himself, appears (Luke 24:36–43). Those present are so "startled" and "frightened," they think Jesus is a spirit. "Startled" is from the Greek root word ptoeō which is related to the word for "fly away." Under a "fight or flight" response, this would be an impulse to run. Emphobos, the Greek root word from which "frightened" is taken, means to be terrified. This is not the first time the disciples have thought Jesus was a spirit. After He fed the five thousand outside of Bethsaida and withdrew to the mountains to pray, He walked past the disciples who were in a boat trying to cross the Sea of Galilee (Mark 6:30–52). Mark says, "…when they saw him walking on the sea they thought it was a ghost…" (Mark 6:49).

It isn't until Jesus presents His pierced hands and feet that the disciples fully believe (John 20:20, 26–27). The disciples have been characterized by hard hearts and preconceived ideas that blind them to Jesus' real purpose. We cannot judge them; we are fortunate that we have the Holy Spirit who will guide us into truth (John 16:13) and testify to our hearts who Jesus is (John 15:26).