Matthew 13:10
Jesus' disciples came and said to Him, "Why are you speaking to them [i.e., the large crowds] by using parables?"
Mark 4:10
And when He was alone those people who gathered around Him, along with the twelve apostles, asked Him what the parables meant.
Mark 4:33-34
And He spoke "the word" to them [i.e., the crowds] with as many such parables as they were able to receive.
Treasury of Scripture Knowledge
Summary
And the disciples came, and said unto him, Why speakest thou unto them in parables?