Answer
In John 12:37–40, the apostle emphasizes the relationship between divine sovereignty and human responsibility:
Though he had done so many signs before them, they still did not believe in him, so that the word spoken by the prophet Isaiah might be fulfilled: “Lord, who has believed what he heard from us, and to whom has the arm of the Lord been revealed?” Therefore, they could not believe. For again Isaiah said, “He has blinded their eyes and hardened their heart, lest they see with their eyes, and understand with their heart, and turn, and I would heal them” (ESV).
John’s deliberate inclusion of Old Testament prophecy is important, for he desires to show that Jesus is the long-awaited Messiah and the Son of God.John quotes prophecies contained in Isaiah 53:1 and Isaiah 6:10. The first, from Isaiah 53:1, predicts the servant of the Lord will be rejected by the people in unbelief. That chapter goes on to detail the suffering the servant endures and his eventual exaltation by God. Isaiah 6 relates the calling of Isaiah as a prophet. Verse 10 says the effect of Isaiah’s preaching would be to “harden the hearts of these people” (NLT). So, the people would disbelieve God’s messenger, and the result would be a divine hardening of their hearts (cp. Romans 9:17–18). There is a relationship between divine sovereignty and human responsibility.
On one hand, people are held accountable for their unbelief, as evidenced by John’s statement, “They still would not believe in him” (John 12:37). People have a responsibility to recognize, accept, and believe in the Son of God—especially those who were present to see Jesus’ miracles. At the same time, God plays a role in blinding the eyes and hardening the hearts of unbelievers.
One judgment for rejecting the light is to be blinded to further light. Just prior to the statement that God hardened their hearts is a discussion of the Light they were rejecting:
Then Jesus told them, “You are going to have the light just a little while longer. Walk while you have the light, before darkness overtakes you. Whoever walks in the dark does not know where they are going. Believe in the light while you have the light, so that you may become children of light.” When he had finished speaking, Jesus left and hid himself from them. (John 12:35–36)
They had the Light, but they did not believe in the Light, so the Light was hidden from them. God hardened their hearts as He had done to the rebels in Isaiah’s day.God’s redemptive plan necessitated the people’s rejection of the Son, and Scripture predicted it. Yet that does not absolve anyone of responsibility. “The Son of Man will go as it has been decreed. But woe to that man who betrays him!” (Luke 22:22; cf. Acts 2:23).
Salvation is of the Lord, but we have a responsibility to receive Him by faith: “He came to his own, and his own people did not receive him. But to all who did receive him, who believed in his name, he gave the right to become children of God, who were born, not of blood nor of the will of the flesh nor of the will of man, but of God” (John 1:11–13, ESV).
God is ultimately sovereign over everything, including disbelief, but people are still responsible for their rejection of Christ. We may never fully understand how divine sovereignty and human responsibility are compatible, but we can trust that the Lord is good and He “works for the good of those who love him, who have been called according to his purpose” (Romans 8:28).