Matthew 13:11-15

Mat 13:11 (KJB)
He answered and said unto them, Because it is given unto you to know the mysteries of the kingdom of heaven, but to them it is not given.

Here Jesus states to the disciples that the mysteries of the Kingdom of Heaven will be given only to those whom the Lord Jesus saves but to the rest of the unbelieving world, the mysteries of that Kingdom are withheld. This is a form of election where only those who are saved are privileged to know the mysteries while the unsaved will never come to the truth of these mysteries. Divine truths are considered mysteries because apart from the indwelling Holy Spirit, a person will be unable to understand them. When it speaks of the Kingdom of Heaven here, it also includes all aspects of the Gospel. (Eph 3:4 KJV) Whereby, when ye read, ye may understand my knowledge in the mystery of Christ) Another mystery is the mystery of Christ who was withheld in times past but is now revealed. That revelation is for the believers only as we saw that the Pharisees, who were supposed to be experts in the law and the Scriptures, did not recognize Christ because He was the mystery withheld.

Mat 13:12 (KJB)
For whosoever hath, to him shall be given, and he shall have more abundance: but whosoever hath not, from him shall be taken away even that he hath.

Then Jesus gives a spiritual principle. Those who have become saved and understand the Gospel will have their understanding increased to the point that they will have abundant understanding. Of course, this came with the filling of the Holy Spirit on Pentecost and right after that we saw the disciples preaching the fulness of the Gospel and the whole story like Stephen and Peter. (Prov 9:9 KJV) Give instruction to a wise man, and he will be yet wiser: teach a just man, and he will increase in learning. Then Jesus gives the other side of the story and that those who have not, which are those who are unsaved, shall have taken from them even what they have.  That is, those who have the external façade of religiosity and think that they have understanding will become more apostate in their views and will walk farther away from God. In the final analysis, all their religion and knowledge will not help them because they will stand in the judgment and since they are found false, will be cast into the lake of fire and thus what they had is taken from them such as false assurance of Heaven.

Mat 13:13 (KJB)
Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand.

This second answer of Jesus basically resembles the first. Jesus had done amazing miracles from healing the sick to raising the dead right in their presence but they had rejected the works and His teachings. Since they had shown themselves to be rebellious, Jesus now spoke to them in parables. It was not because they could not hear, see, or understand since many miracles were done right in their sight but the fact was their hearts were so hardened, that they would not see, hear, or understand. It was willful rebellion which caused this situation.

Mat 13:14 (KJB)
And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive:

Here we have the commission of Isaiah and the ministry of Jesus in parallel. (Isa 6:9 KJV) And he said, Go, and tell this people, Hear ye indeed, but understand not; and see ye indeed, but perceive not. When Isaiah was commissioned to be a prophet to Judah, right at the outset God told him that the people he was going to minister to would reject him because their hearts had become so hardened. They would hear his message but would not be able to understand it. They would see but would be unable to comprehend what they were seeing that God would send a prophet to them to bring them back so they would not face the same judgment as the Northern Kingdom.

Mat 13:15 (KJB)
For this people's heart is waxed gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes and hear with their ears, and should understand with their heart, and should be converted, and I should heal them.

(Isa 6:10 KJV) Make the heart of this people fat, and make their ears heavy, and shut their eyes; lest they see with their eyes, and hear with their ears, and understand with their heart, and convert, and be healed. God had basically told Isaiah that is to metaphorically put a band of fat around their hearts so the truth will be unable to penetrate it. This would make the message of Isaiah more unreceptive as God’s message and word. The word in the Greek for “waxed gross” basically carries the same meaning as that of the Hebrew in Isaiah. It means to “make fat or thicken.” Their ears had become dull of hearing. The word “dull” carries with it the meaning of “heavy.” It can be understood like when you are tired and your eyelids begin to feel heavy and then they start to close. Their ears had become so heavy that their ears were closed to the message of both Jesus and Isaiah. Then their eyes were also closed to the Gospel. Even though they had seen the miracles Jesus did, their eyes were closed to the reality of what took place.

The second half of this verse gives the condition that the people were in. (Exo 4:21 KJV) And the LORD said unto Moses, When thou goest to return into Egypt, see that thou do all those wonders before Pharaoh, which I have put in thine hand: but I will harden his heart, that he shall not let the people go. They were so calloused toward the true Gospel, that their hearts were hardened whenever they heard the Gospel. Just as God hardened the heart of Pharaoh, He hardens the heart of those who refuse to hear the Gospel causing them to become more opposed to the Gospel. The people that Jesus was speaking to in parables were just that way. Their hearts were hardened by the teaching of the Pharisees for many years and that band of fat around their heart was made very thick. By themselves, they would be unable to know their lost spiritual condition unless God opened their hearts to the reality of it and then saved them. This is what Jesus did. He took many of the Jews and caused them to be saved and the rest were left in their hardened state. They would not be able to look at other who became saved in Christ and be jealous and desire to be like them on their own. They would have to be regenerated from the outside by the Lord Jesus Christ. This is the doctrine of election at work. By themselves, they could not save themselves but by Christ opening their hearts to their lost spiritual condition, they would then know of their need for a Savior.