He told many stories such as this one:"A farmer went out to plant some seed.
As he scattered it across his field, some seeds fell on a footpath, and the birds came and ate them.
Other seeds fell on shallow soil with underlying rock. The plants sprang up quickly,
but they soon wilted beneath the hot sun and died because the roots had no nourishment in the shallow soil.
Other seeds fell among thorns that shot up and choked out the tender blades.
But some seeds fell on fertile soil and produced a crop that was thirty, sixty, and even a hundred times as much as had been planted.
Anyone who is willing to hear should listen and understand!"
His disciples came and asked him, "Why do you always tell stories when you talk to the people?"
Then he explained to them, "You have been permitted to understand the secrets of the Kingdom of Heaven, but others have not.
To those who are open to my teaching, more understanding will be given, and they will have an abundance of knowledge. But to those who are not listening, even what they have will be taken away from them.
That is why I tell these stories, because people see what I do, but they don't really see. They hear what I say, but they don't really hear, and they don't understand.
This fulfills the prophecy of Isaiah, which says: 'You will hear my words, but you will not understand; you will see what I do, but you will not perceive its meaning.
For the hearts of these people are hardened, and their ears cannot hear, and they have closed their eyes -- so their eyes cannot see, and their ears cannot hear, and their hearts cannot understand, and they cannot turn to me and let me heal them.'
References for Matthew 13:15
"But blessed are your eyes, because they see; and your ears, because they hear.
I assure you, many prophets and godly people have longed to see and hear what you have seen and heard, but they could not.
"Now here is the explanation of the story I told about the farmer sowing grain:
The seed that fell on the hard path represents those who hear the Good News about the Kingdom and don't understand it. Then the evil one comes and snatches the seed away from their hearts.
The rocky soil represents those who hear the message and receive it with joy.
But like young plants in such soil, their roots don't go very deep. At first they get along fine, but they wilt as soon as they have problems or are persecuted because they believe the word.
The thorny ground represents those who hear and accept the Good News, but all too quickly the message is crowded out by the cares of this life and the lure of wealth, so no crop is produced.
The good soil represents the hearts of those who truly accept God's message and produce a huge harvest -- thirty, sixty, or even a hundred times as much as had been planted."