Matthew 13:10
Then the disciples came and asked Jesus, "Why do you speak to people in parables?"
Mark 4:10
When he was alone with the Twelve and those around him, they began to ask him about the parables.
Mark 4:33-34
With many other parables like these, Jesus kept speaking his message to them according to their ability to understand.
Treasury of Scripture Knowledge
Summary
And the disciples came, and said unto him, Why speakest thou unto them in parables?