With many such parables he spoke the word to them, as they were able to hear it. He did not speak to them without a parable, but privately to his own disciples he explained everything.
(Mark 4:33-34 ESV)
And when he was alone, those around him with the twelve asked him about the parables. And he said to them, “To you has been given the secret of the kingdom of God, but for those outside everything is in parables, so that
“they may indeed see but not perceive,
and may indeed hear but not understand,
lest they should turn and be forgiven.”
(Mark 4:10-12 ESV)