Matthew 13:10
Then the disciples came to him and said, "Why do you speak to them in parables?"
Mark 4:10
When he was alone, those around him with the twelve asked him about the parables.
Mark 4:33-34
So with many parables like these, he spoke the word to them, as they were able to hear.
Treasury of Scripture Knowledge
Summary
And the disciples came, and said unto him, Why speakest thou unto them in parables?