39 Therefore they could not believe, because Isaiah said again:
Verses 39-41 tie the unbelief of Israel in Jesus’ day to Isaiah 6:10. Isaiah predicted Israel’s rejection of Jesus and their divine judicial hardening. God Himself blinded their eyes and hardened their hearts.
Isaiah 6 is about Isaiah’s own coming to grips with the majesty of the Lord and his offer to serve the Lord. However, Jehovah warned Isaiah that people would reject his message. God Himself would further harden their hearts because of this. Jehovah clearly demonstrated the entrenched negative volition of Israel by doing this.
Verse 39 is a solemn statement about the nature of Israel’s unbelief. They reached a point where they “could not believe.” In face of indubitable evidence presented to them by Jesus, they still rejected Him as the Messiah. God did everything necessary to present the credentials of Christ to them. The problem lay in their hearts and sinful orientation.
“Therefore” looks forward. The reason these people could not believe was because of verse 40. It was not that their unbelief was a fulfillment of prophecy, but that prophecy occasioned their unbelief.
they could not believe,
Having been warned that the people of Isaiah’s day ignored revelation that came through Isaiah, the nation Israel in Jesus’ day would not believe Jesus’ revelation either. They “could not” believe or they were unable to believe. The reason they “could not” believe was they rejected every means of supernatural revelation from God.
The unbelief of Israel was so persistent that they reached a point where they could not any longer believe. They could not believe, not because God would remove their freedom of choice, but because their volition was entrenched in unbelief. God gave them over to their negative volition. They “could not” believe because they would not believe.
Unbelief was a punishment by God for their hardness toward His Word. Persistent unbelief was the cause of God’s judicial hardening of Israel (Ro 9:17).
because Isaiah said again:
The next verse is a quote from Isaiah 6:10. Both Jesus (Mt 13:14-15; Mr 4:12; Lu 8:10) and Paul (Ac 28:26-27) cited this verse. This ascribes the quote to God’s will against persistent unbelief. Unless God is active in belief, there is nothing to it. This verse in Isaiah follows a series of prophetic warnings.
Isaiah 6 gave account of Isaiah’s commission to ministry. God called him to prophesy during the declining of the kingdom of Judah but warned him that his message would be rejected. Just as Isaiah’s message would be rejected, so Israel would decline Jesus’ message.
God never forces His will on people.
It is important that we understand that this passage does not argue for God’s hardening of people before they had a chance to believe in Christ. God does not force His absolute will on people. This is a judicial declaration of His will upon those who stubbornly reject His message.
God involves Himself in the consequences of our choices. He does this progressively. The further we go negative to His revelation, the more He allows us to develop a reprobate mind (Ro 1:24, 26, 28).
God persistently and sovereignly involves Himself in our decisions. God’s hand is in everything, in every process, in every act, and in every thought that we might have. This, again, is the doctrine that God sovereignly concurs with everything in our lives exhaustively. He is never frustrated by our choices because He manages events, people, and everything that helps us to make a decision about things. He will accomplish His will, whether by our positive volition or negative volition. All of these actions by God may or may not be seen or observed by people.