When he was alone, those around him with the Twelve asked him about the parables. He answered them, “The secret of the kingdom of God has been given to you, but to those outside, everything comes in parables so that
they may indeed look,
and yet not perceive;
they may indeed listen,
and yet not understand;
otherwise, they might turn back
and be forgiven.”
It sounds like Jesus is saying that he doesn’t want outsiders to get it and be forgiven, saved or healed. He quotes Isaiah 6, Isaiah’s commission, after Isaiah says to God, “Here I am send me”. God’s answer is, “Okay, I will send you, to speak to my people, but they won’t listen to you”. God wants his people to repent, to be forgiven, but they refuse. He is not saying that he has made them this way or caused it, but it is their choice. Was Isaiah and now Jesus trying to prevent people from hearing and responding to God’s message, and avoid destruction? No, not at all. Instead, what we have here is the Hebrew or Jewish style of expressing a consequence as though it were a purpose (FF Bruce, Hard Sayings of Jesus / Hard sayings of the Bible pp.417-8). It is sort of like saying, “You’re not going to believe this but…”, and then you tell them the truth or what’s real. But there is room for a person to still believe.
The interpretive key is verse 20 of Mark 4:
And those like seed sown on good ground hear the word, welcome it, and produce fruit thirty, sixty, and a hundred times what was sown.
These ones hear the word and welcome it: their choice.
Revelation enlightens the receptive, but befuddles the unreceptive (1 Cor. 2:6-16). The inability to comprehend is a judgement of unbelief (Rom. 11:25-32). (Constable’s notes)
The context in which Isaiah’s words are quoted, help us understand why he said this. In the previous chapter, shocking unbelief and opposition to Jesus was reported: They platted to kill Jesus (3:6) and that he is working with the demonic (3:22).
The background or underlying principle of parables is that when God reveals himself to people, they either accept or reject him. The parable is a riddle that contains revelation to the receptive, but enigma to the hard of heart.
And the quote from Isaiah does not mean that outsiders (unsaved, unrepentant people) are doomed and denied the possibility of having their hearts healed, but it expresses the idea that they simply can not, they are barred from the secrets, the knowledge of the Kingdom, because of and so long as their unbelief remains. One must exercise, decide to have faith; which only comes through grace freely offered by God. The person who does not accept God’s grace when presented with divine revelation receives the judgement of a blind, hard heart that can not understand what God is saying (William Lane, Mark, pp.158-9).
I wrote a whole post on the parable of the sower: