Jesus’s use of Isaiah 6:9-10 in describing his use of parables has presented a challenge for many interpreters in understand the intent or purpose of parables. Isaiah said,
Isaiah 6:9–10 (ESV) — 9 And he said, “Go, and say to this people: “ ‘Keep on hearing, but do not understand; keep on seeing, but do not perceive.’ 10 Make the heart of this people dull, and their ears heavy, and blind their eyes; lest they see with their eyes, and hear with their ears, and understand with their hearts, and turn and be healed.”
All 3 synoptic Gospels contain Jesus’s reference to this Isaianic passage, albeit with some variation. I think Hendriksen and Kistemaker offer some helpful observations as follows:
When Luke writes, “that seeing, they may not see,” etc., he is reproducing the words of Isa. 6:9, 10 in greatly abbreviated form. One might also say, “Luke, having before him Mark’s already abbreviated reproduction of Isaiah’s words, abbreviates them still further.” The most complete quotation is found in Matt. 13:13–15.
There is a difference, however, between Matthew’s reproduction and that of Mark-Luke. Matthew states that Jesus made use of parables because the people’s heart had become dull, their ears hard of hearing, etc. Mark-Luke changes this “because” or “for” into “that” or “in order that.” Which report is right, Matthew’s or Mark-Luke’s?
The answer is: “Both are correct.” It was because by their own choice these impenitent Pharisees and their followers had refused to see and hear, that, as a punishment for this refusal, they are now addressed in parables, “that [or in order that] seeing, they may not see; and hearing, they may not understand. They must “endure the blame of their own blindness and hardness” (Calvin on this passage). God had given these people a wonderful opportunity; but they had refused to avail themselves of it. Result: it is God’s sovereign will to remove what man is unwilling to improve, to darken the heart that refuses to hearken. He hardens those that have hardened themselves. If God even surrenders to the lusts of their hearts the unenlightened heathen when they hold back the truth in unrighteousness (Rom. 1:18, 26), will he not punish more severely the impenitents before whom the Light of the world is constantly confirming the truthfulness of his message? And if he blesses those who accept the mysterious, will he not curse those who reject the obvious? It is evident, therefore, that Matt. 13:13 is in harmony with Mark 4:12 and Luke 8:10; in fact, the “because” of the former helps to explain the “that” or “in order that” of the latter. When, of their own accord and after repeated threats and promises, people reject the Lord and spurn his messages, then he hardens them, in order that those who were not willing to repent will not be able to repent and be forgiven.
 Hendriksen, W., & Kistemaker, S. J. (1953-2001). Vol. 11: New Testament commentary : Exposition of the Gospel According to Luke. New Testament Commentary (425). Grand Rapids: Baker Book House.
© 2012, Rick Hogaboam. All rights reserved.