Matthew 13:10 "And the disciples came, and said unto him, Why speakest thou unto them in parables?"
Matthew 13:11 "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."
What is a mystery? It is something that is unknown. The answer may be in plain sight, only if you cannot put all the details together, and take all the clues and give an understanding to them, you do not know. There are things dealing with the kingdom of heaven that seem foolish to mankind, and will always remain hidden, unless the Spirit of the Living God reveals them to you.
Today, because those things are mysteries, mankind is going to great lengths to understand the past, when all the time it is written in His Word. However, those truths cannot be understood because it is God that has blinded them for their own protection. Why would this be? Because if they had the understanding, and were tried by the Antichrist Satan, and his system, (which is coming shortly), they would not have the ability to stand against Satan. They lack faith and willpower to turn themselves over completely to the Holy Spirit. They just don't care, and they continue to live in a state of hopelessness.
Matthew 13:12 "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."
What are we talking about here? The Word of God! If a certain amount is given to you, can you sow it, and replant it in someone's mind? If you do not sow the Word of God in another persons mind, then God will take the understanding that He has given you, and and He will allow you to become deceived in the ways of the world, just as if you never received the Word in the first place. If you have a truth, share it with someone else, or you will lose it.
Matthew 13:13 "Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand."
Matthew 13:14 "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:"
This was prophesied by Isaiah in Isaiah 6:9, 10; "And he said, Go, and tell this people, Hear ye indeed, but understand not; and see ye indeed, but perceive not. [9] 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.[10]."
Our Heavenly Father has sent us His Son, and He performed many great miracles in their sight, and yet these blind and dumb scribes and Pharisees, after seeing and hearing Christ with His many wonderful acts yelled out, "show us a sign". Though they saw with their eyes and heard with their ears, they understood nothing that was going on around them. Their minds were closed, and they perceived nothing. Jesus is saying it here, Paul said it later, and the prophet Isaiah said it five hundred years prior to Jesus Christ's birth; "these people" are in a stupor. We will find out later who "these people" are with the "fat hearts", or thick minds.
Matthew 13:15 " 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."
Jesus gave us many prophesies and rich teachings, as He walked upon the earth, and all the time these scribes and Pharisees, stumbling after Christ missed the whole thing. It's like they went to the ball game, and were more concerned with the lead in the paint on the scoreboard, then the score posted. It was written long ago, many times, by the prophets, and in the sky that the Messiah would come, and when He came He performed the prophesies, and performed the miracles so that those with eyes to see and ears to hear would understand.
God didn't close their eyes, they closed them themselves, then God sent the stupor. They made the choice, and then God acted on their choice. This is also what will happen again very shortly. Those who choose to study and know the truth will be sealed in their minds with the understanding of God and His prophecies of the end times, And those who choose to believe Satan's lies, God will send them into a stupor, and they will be deceived.
http://www.theseason.org/matthew/matthew13.htm