Mark 4:33
And He spoke "the word" to them [i.e., the crowds] with as many such parables as they were able to receive.
John 16:12
"I still have many things to tell you, but you cannot bear [to hear] them at present.
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.
1 Corinthians 3:1-2
And I could not speak to you, brothers, as I would to spiritual people, but [I have to speak to you] as I would to worldly people, for you are immature children in [the fellowship of] Christ.
Hebrews 5:11-14
[Now] we have many things to say about Melchizedek, but because of your slowness to grasp things, they are hard to explain.