10 And the disciples came and said to Him, “Why do You speak to them in parables?”
11 He answered and said to them, “Because it has been given to you to know the mysteries of the kingdom of heaven, but to them it has not been given.
12 For whoever has, to him more will be given, and he will have abundance; but whoever does not have, even what he has will be taken away from him.
13 Therefore I speak to them in parables, because seeing they do not see, and hearing they do not hear, nor do they understand.
14 And in them the prophecy of Isaiah is fulfilled, which says: ‘Hearing you will hear and shall not understand, and seeing you will see and not perceive;
15 For the hearts of this people have grown dull. Their ears are hard of hearing, and their eyes they have closed, lest they should see with their eyes and hear with their ears, lest they should understand with their hearts and turn, so that I should heal them.’
16 But blessed are your eyes for they see, and your ears for they hear;
17 for assuredly, I say to you that many prophets and righteous men desired to see what you see, and did not see it, and to hear what you hear, and did not hear it.
seeing they do not see (v.13) — they did not wish to see — or hear or understand
The quote (v.14) is from Isaiah 6:9-10 in the Septuagint.
dull (v.15) = fat
The people, notwithstanding His ministry, had rejected Him up to this time, and therefore He could not give to them, nor could they have received, the mysteries of the Kingdom. To the men who had crowned Him, He belonged; and all the principles and privileges of the Kingdom they were able to appreciate and possess. The others had so far refused their allegiance and were therefore unable to see, or enter into, the Kingdom.
If we go further back for a moment, we may state the case thus. All these men among whom the ministry of Jesus had been exercised had preliminary knowledge of the ways of God as a result of the religion in which they had been born and trained. In fulfillment of the messages of their own Scriptures He had come. Certain of them had received Him, others of them had rejected Him. To those receiving Him were given the mysteries of the Kingdom. to those rejecting Him these messages could not be given, and they were in danger of losing the real value of all that they had gained through their early religious training. — Morgan, page 141.
It was never God’s desire to harden anyone’s heart or to close anyone’s eyes against the truth, but it is a principle that runs throughout the word of God that the truth either softens or hardens. The very same sun that softens the wax hardens the clay; and so the very same gospel message which breaks down honest hearts and leads to repentance, hardens the hearts of the dishonest and confirms them in their path of disobedience. — Ironside, page 163.
The unbelievers could not grasp the new revelation about the kingdom because they would not grasp the revelation already given.
Most of my commentaries claim the kingdom the Lord was teaching about here is the current age, between His resurrection and His second coming. This is demonstrably wrong for several reasons. I’ll mention two.
First, verse 17 says that the prophets desired to see what the apostles were seeing. Since the prophets hadn’t known anything about the current age (as evidenced by the misunderstanding nearly everyone had about the Messiah’s suffering), they couldn’t have desired to know more. Their desire must have been related to some truth that was revealed to them in some degree — namely, the Millennial Kingdom.
Second, while John the Baptist and the Lord preached that the Kingdom was at hand — or close — because the Messiah was at hand, they never said it was here. Again, this is because of the misunderstanding about the necessity of the Messiah to suffer and die. It was only after that occurred that the Kingdom could be — and was — offered, in Acts 2. So, it makes no sense that Christ would have moved on to teaching about what is to take place after the Jews rejected the Kingdom before the Kingdom was even offered and their rejection wasn’t final.
The mystery of the current age, during which the Kingdom would be delayed, was still a mystery until the truth was given to Paul after the Jew’s final rejection of the Messiah when Steven was put to death.