Mark’s Jesus spoke in parables so outsiders would not understand what he was saying.

If outsiders were to understand, they would repent. The other gospels lack this passage.

Mark 4:10-12 As soon as Jesus was alone with the Twelve and those around Him, they asked Him about the parable.

He told them, “The mystery of the kingdom of God has been given to you, but to those on the outside, everything is expressed in parables, so that ‘they may be ever seeing but never perceiving, and ever hearing but never understanding; otherwise they might turn and be forgiven.’”