In this passage, Paul quotes from the prophet Isaiah saying:
"The Holy Spirit spoke the truth to your forefathers when he said through Isaiah the prophet: "'Go to this people and say, "You will be ever hearing but never understanding; you will be ever seeing but never perceiving."For this people's heart has become calloused; they hardly hear with their ears, and they have closed their eyes. Otherwise they might see with their eyes, hear with their ears, understand with their hearts and turn, and I would heal them.' "Therefore I want you to know that God's salvation has been sent to the Gentiles, and they (also) will hear it!"
I don't believe Paul was casting off the responsibility to proclaim the good news to the Jewish people, rather, he was appealing to them to listen and letting them know they were not the only recipients of God's plan of salvation.
Throughout Jesus teaching ministry it was not uncommon for him to say "Whoever has ears to hear, let him hear." I see us in the same dangerous situation of hearing but not understanding, seeing, but not perceiving as Paul's audience was then. We are so saturated with the word of God and the teachings of Christ, it is easy to think we have a handle on what they mean and stop listening.
Jesus issued this warning in a parable he told in Matthew 7:24-28 "Therefore everyone who hears these words of mine and puts them into practice is like a wise man who built his house on the rock. The rain came down, the streams rose, and the winds blew and beat against that house; yet it did not fall, because it had its foundation on the rock. But everyone who hears these words of mine and does not put them into practice is like a foolish man who built his house on sand. The rain came down, the streams rose, and the winds blew and beat against that house, and it fell with a great crash."
Jesus tells us that the ability to walk through life's trials and hardships is determined by whether we take to heart what he says. Whether we not only hear, but stop to consider his teaching and allow it to permeate our lives.
James also has something to say about listening to the word. James 1:22-25 "Do not merely listen to the word, and so deceive yourselves. Do what it says. Anyone who listens to the word but does not do what it says is like a man who looks at his face in a mirror and, after looking at himself, goes away and immediately forgets what he looks like. But the man who looks intently into the perfect law that gives freedom, and continues to do this, not forgetting what he has heard, but doing it--he will be blessed in what he does."
If we surround ourselves with God's word, and Jesus' teachings, and we do not allow them to affect change in our lives, we are like a foolish person who sees his own faults in a mirror and does nothing to correct them. We can choose to allow God's word to come in and do a work in our lives, or we can choose to walk away. Only one of those choices carries with it blessings.
John, in Revelations sends word to seven churches, and to each one, he says, "He who has an ear, let him hear what the Spirit says to the churches," followed with promises to those who overcome because of their hearing and obeying the word of the Spirit. Those promises include: the right to eat from the tree of life, not suffering the second death, a new name, authority over the nations, being dressed in white and acknowledged before the Father, being a pillar in the temple, and sitting on the throne with Jesus. All of this overcoming is accomplished through nothing other than hearing the words of Christ and allowing him to apply them to our lives.
Sometimes it is difficult to know just how Jesus' words need to be applied in us. For those times, Jesus says to his disciples, "I have set an example for you to do as I have done"(John 13:15). He was talking about the example he set in washing their feet, but it applies more broadly to everything that he did in front of them as an example of how they, and we, should live. When we look at the life of Christ, dominated by the law of love, we can see how he lived out the things that he taught. We cannot do all the things that he did--he is the Son of the Living God, but Jesus said that we would do even greater things than he had done through the Holy Spirit. Walking in step with him, hearing and taking his words to heart, allowing the law of love to rule in our lives, these are the keys to victorious living in Christ. And to those who overcome, there will be inexpressible blessing in heaven with him!