Jesus explains his parable
10 When they were alone, the people around Jesus, along with the Twelve, asked him about the parables. 11 He said to them, “The secret of God’s kingdom has been given to you, but to those who are outside everything comes in parables. 12 This is so that they can look and see but have no insight, and they can hear but not understand. Otherwise, they might turn their lives around and be forgiven.
https://www.biblegateway.com/passage/?search=Mark%204&version=CEB