10 Then the disciples came and said to him, "Why do you speak to them in parables?"  11 And he answered them, "To you it has been given to know the secrets of the kingdom of heaven, but to them it has not been given.
12 For to the one who has, more will be given, and he will have an abundance, but from the one who has not, even what he has will be taken away. 13 This is why I speak to them in parables, because seeing they do not see, and hearing they do not hear, nor do they understand.
14 Indeed, in their case the prophecy of Isaiah is fulfilled that says: "'You will indeed hear but never understand, and you will indeed see but never perceive. 15 For this people's heart has grown dull, and with their ears they can barely hear, and their eyes they have closed, lest they should see with their eyes and hear with their ears and understand with their heart and turn, and I would heal them.' 16 But blessed are your eyes, for they see, and your ears, for they hear. 17 Truly, I say to you, many prophets and righteous people longed to see what you see, and did not see it, and to hear what you hear, and did not hear it." 

Matthew 13:10-17 (ESV)