Mark 4:11
He said to them, "You disciples are being given an understanding of the secret of the kingdom of God, but to outsiders everything will be told in parables.
Matthew 13:10-17
Jesus' disciples came and said to Him, "Why are you speaking to them [i.e., the large crowds] by using parables?"
Matthew 13:34-35
Jesus spoke all these things to the crowds with parables. He did not say anything to them without using a parable.
Matthew 13:51-52
"Have you understood all these things?" [Jesus asked]. "Yes," they said to Him.
Mark 4:34
And He did not speak to them [i.e., concerning the kingdom] without using a parable, but He explained everything to His own disciples privately.
Acts 8:30-31
So, Philip ran over to it and [when he got near enough] he heard the Ethiopian eunuch reading from Isaiah the prophet and asked him, "Do you understand what you are reading?"
Hebrews 5:14
But "solid food" is for mature people, who because of using their [spiritual] senses, have become able to distinguish good from evil.
2 Peter 3:16
He spoke about these things in all of his letters, which contain some parts that are difficult to understand. [Because of this], ignorant and unstable people twist [his writings], just as they also do to the other Scriptures, to their own destruction.