Contradiction with Matthew 14:26
Mark 6:49 states they thought they saw a spirit, similar to Matthew 14:26, but Matthew explicitly clarifies their cry of fear, omitting the assurance given in Mark 6:50.
Matthew 14:26: And when the disciples saw him walking on the sea, they were troubled, saying, It is a spirit; and they cried out for fear.
Contradiction with Luke 24:37
In Mark 6:49, the disciples are frightened by what they think is a spirit, showing their belief that spirits could somewhat resemble Jesus; however, Luke 24:37 describes their disbelief and fear upon seeing Jesus after His resurrection, contrary to their immediate recognition.
Luke 24:37: But they were terrified and affrighted, and supposed that they had seen a spirit.
Contradiction with John 6:21
Mark 6:49 describes fear and misunderstanding upon seeing Jesus, but John 6:21 emphasizes them willingly receiving Him into the ship, indicating a resolution of fear that's less pronounced in Mark.
John 6:21: Then they willingly received him into the ship: and immediately the ship was at the land whither they went.
Contradiction with 1 John 4:1
Mark 6:49 highlights the disciples’ fear of spirits and immediate conclusion; 1 John 4:1 advises testing the spirits, which contrasts with the disciples' initial reaction of fear without discernment.
1 John 4:1: Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world.