John 12:39 explains that the people who refused to believe in Jesus were not able to believe, and John says this was fulfilled what the prophet Isaiah had already foretold. The verse is John’s own comment on the unbelief that surrounded Jesus during his public ministry. It is spoken by the Gospel writer, John, who is looking back over the events of Jesus’s life and connecting them to the Old Testament prophets.
For this cause they couldn’t believe, for Isaiah said again…
John 12:39 (WEB)
What John 12:39 Means
The phrase “for this cause they couldn’t believe” points backward to the events just before it. John has just described how Jesus had performed many signs in front of the crowd, yet they still did not trust him. John’s answer is that their unbelief was not a surprise to God. It fit a pattern the prophets had described long before.
The word “cause” here does not mean that God forced people into unbelief in a simple, mechanical way. Rather, John is saying that the unbelief of Jesus’s hearers was part of a larger story that Scripture had already told. The verse does not promise that every person who hears the gospel will believe, and it does not explain every individual’s reasons. It shows that God’s purposes were at work even in the rejection of his Son.
The Context of John 12:39
John wrote this Gospel to show that Jesus is the Christ, the Son of God, and that those who believe in him receive life. Its readers were largely early Christians, and many of them had Jewish backgrounds, so John often cites the Hebrew Scriptures to show that Jesus fulfilled them. Verses 36 through 42 form a section where Jesus withdraws from the crowd, and John reflects on why so many still refused him.
Just before verse 39, John quotes Isaiah 53:1 in verse 38, asking who has believed the message of the Lord. Verse 40 then quotes Isaiah 6:10 about hearts being hardened. Seen in this setting, verse 39 is the bridge between the two quotations. It tells the reader that the unbelief John has described is what Isaiah had already spoken about, and that this does not contradict the offer of the gospel.
Key Phrases in John 12:39
Isaiah 6:10
Make the heart of this people fat. Make their ears heavy, and shut their eyes; lest they see with their eyes, and hear with their ears, and understand with their heart, and turn again, and be healed.”
(WEB)
This is the passage John echoes in verse 40. Reading it in its original setting shows how the prophet described a hardening of hearts within Israel, and it helps clarify the meaning of the phrase that John applies to Jesus’s ministry.
Ephesians 2:8
For by grace you have been saved through faith, and that not of yourselves; it is the gift of God…
(WEB)
Paul teaches that salvation and the faith that receives it are a gift from God. This verse balances John 12:39 by showing that belief is ultimately the work of grace, and it encourages believers to trust God’s initiative in bringing people to faith.
A Short Prayer From John 12:39
Lord, you know the hearts of every person, including the ones that feel closed to you and including my own. When I see people who cannot seem to believe, I ask you to be at work in them in ways I cannot see. When my own faith feels weak or stubborn, I ask you to soften what has grown hard in me. Help me to speak with honesty and love, and to trust you with the results. Open our eyes to see your glory in Jesus, and give us the grace to believe. Amen.
