When Jesus was alone with his disciples, they came up and said to him “Why do you speak to people in parables? What does the parable of the sower mean?”
Jesus answered them “The mystery of the kingdom of God has been revealed to you but not to everyone. For them the information is transmitted in parables so that Isaiah’s prophecy is fulfilled. It says ‘They may listen but never understand, and they may look and never see. For people’s hearts have grown hard and their ears have grown deaf, and they have closed their eyes, otherwise they might see, hear, and understand and turn back, and I would heal them.'”
MT 13:10-15, MK 4:10-12, LK 8:9-10.