So they began to leave, unable to agree among themselves, after Paul made one last statement: “The Holy Spirit spoke rightly to your ancestors through the prophet Isaiah when he said, ‘Go to this people and say, “You will keep on hearing, but will never understand, and you will keep on looking, but will never perceive. For the heart of this people has become dull, and their ears are hard of hearing, and they have closed their eyes, so that they would not see with their eyes and hear with their ears and understand with their heart and turn, and I would heal them.”‘ “Therefore be advised that this salvation from God has been sent to the Gentiles; they will listen!” [When he had said these things, the Jews departed, having a great dispute among themselves.] —Acts 28:25-29
The outcome of this meeting reminds me of Paul’s trial before the Sanhedrin, when some (Pharisees) sided with Paul, and the rest strongly opposed him. In verse 25, Luke tells us that these Jews disagreed among themselves about what Paul had taught. A number of translations do not regard verse 29 as a part of the original text because it is missing in some key manuscripts. This verse simply reiterates Luke’s statement in verse 25, even more emphatically.
As they are beginning to leave, Paul adds one more thing and cites Isaiah 6:9-10 as a fitting explanation of their response to the gospel. This quotation is even more meaningful when you remember that our Lord cited this same text in every one of the four Gospels. In Matthew (13:14-15), Mark (4:12), and Luke (8:10), Jesus cited this text He was explaining why He began to teach the people in parables. In effect, Jesus was saying, “I am speaking to them in parables so that they won’t understand Me, won’t repent, and thus won’t be saved.”
This seems like a horrible thing to say, until you consider the context, and understand why Jesus said this. Jesus had been performing many miracles to underscore the authenticity of His teaching. Initially, the Jewish leaders who opposed Jesus tried to discredit thes miracles as being something less than miraculous. However, when the authenticity of the miracles became undeniable, the scribes from Jerusalem took a different approach: they claimed that our Lord’s miraculous power was actually from the devil. In other words, in their minds, Jesus was demon possessed.
The experts in the law who came down from Jerusalem said, “He is possessed by Beelzebul,” and, “By the ruler of demons he casts out demons” —Mark 3:22
Jesus responded that while every blasphemy against Him could be forgiven, they had blasphemed against the Holy Spirit, and this sin would never be forgiven. This blasphemy (attributing the work of the Holy Spirit in Jesus to the devil) was the unpardonable sin. This sin was unforgivable, so Jesus spoke in parables to keep them from understanding the gospel and repenting. They had passed the point of no return.
If interested, you can download the entire study of The Story of Acts