Shortly after He delivered "The Parable of the Sower," Jesus' disciples asked Him - "Why do You speak to them in parables?" (Matt. 13:10). He began to answer their question in the next verse - "It has been given to you to know the mysteries of the kingdom of heaven, but to them it has not been given" (Matt. 13:11). A primary reason for speaking in parables was to separate the spiritually minded listeners from the unbelievers. This distinction was not randomly made or predetermined by God to include certain individuals and exclude others. Jesus spoke in parables because they veiled the truth to those who weren't honestly searching for it and revealed the truth to those who readily desired it and were willing to intellectually labor for it.
What did Jesus mean when He mentioned "mysteries of the kingdom of heaven"? The word "mystery" in our current language means that which is not understood, but, as used in the Scriptures, it refers to that which is not understood simply because it has not been divinely revealed. The "mysteries" of which the Bible speaks are not unraveled by science; they are unfolded by revelation (cf. Col. 1:26).
Matthew 13:12 says - "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" (cf. Luke 8:18; Matt. 25:29). The teachings of Jesus are under discussion here. In the beginning of His ministry, Jesus taught plainly, and all His hearers had an equal opportunity to know His doctrine and believe in Him. But, from this point on His teaching would be largely veiled in parables. These parables would enrich the knowledge and understanding of the believers, but they would not be helpful to the unbelievers who were close-minded. The efforts of the unbelievers to understand the parables would withdraw their minds from the truths they had already learned; thus, they would either forget them or fail to profit by them. If man takes advantage of his opportunities (whatever they may be), then other opportunities that are even greater will be created. But, if he is negligent then even the initial opportunities will be taken away. The Pharisees are a sad example of this. They made it plain in Matthew 12 that they would interpret in an evil manner anything Jesus said or did; they chose to be blind and deaf to the truth.
Jesus draws a conclusion in Matthew 13:13 - "Therefore I speak to them in parables, because seeing they do not see, and hearing they do not hear, nor do they understand." The unbelievers saw Christ's miracles, but not in their true light; they heard His words, but didn't comprehend their true meaning. Consequently, some have described parables as a shell that keeps good fruit for the diligent but from the slothful. There is nothing unfair about this method of teaching because ultimately the only ones who cannot perceive the truth within parables are those who condition themselves not to perceive it. When Jesus said that "they do not hear, nor do they understand", He meant that not only did the unbelievers not understand Jesus' teachings, they didn't even listen with the intent of obeying (they didn't "hear")!
We will finish discussing this section of text tomorrow.