Isaiah 29:13 rebukes lip-service with hearts far from God — explaining why the people cannot understand the message of 6:9.

Isaiah 43:8 uses the same 'eyes but blind, ears but deaf' metaphor, reinforcing the theme of spiritual blindness in Isaiah 6:9.

Isaiah 44:18-20 describes idolaters with eyes plastered over, directly echoing the inability to see and understand from Isaiah 6:9.

Isaiah 29:10 says God poured out a spirit of deep sleep and closed eyes — directly echoing the divine blinding in Isaiah 6:9.

Isaiah 48:8 directly states 'you have neither heard nor understood' — the exact same accusation as in Isaiah 6:9.

Isaiah 42:19 asks who is blind and deaf — referencing spiritual blindness, akin to the condition described in Isaiah 6:9.

Luke 8:10 echoes Isaiah 6:9, using the same 'seeing not see, hearing not understand' to explain the veiling in parables.

Acts 28:27 continues the quote of Isaiah 6:10, reinforcing the hardened heart judgment.

Acts 28:26 quotes Isaiah 6:9 as Paul applies the prophecy to his Jewish audience.

John 12:40 directly quotes Isaiah 6:9-10, linking the hardening to Jesus' rejection.

Matthew 13:14 directly cites Isaiah 6:9 as fulfilled prophecy, showing Jesus' parables fulfill the hardening judgment.

Matthew 13:15 continues the quotation, detailing calloused hearts that prevent repentance — an explicit fulfillment of Isaiah 6:9.

Mark 4:12 cites Isaiah 6:9 to explain the purpose of parables: to prevent understanding and forgiveness, fulfilling Isaiah's prophecy.

In John 12:41, Isaiah is said to have seen Christ's glory and spoken of him, connecting his prophetic commission directly to Jesus.

In Luke 19:42, Jesus laments that things of peace are hidden from Jerusalem's eyes, directly echoing the 'seeing but not perceiving' of Isaiah.

In John 8:43, Jesus directly attributes their lack of understanding to inability to hear his word, a specific parallel to Isaiah 6:9.

In John 9:39, Jesus declares that those who see may become blind, a direct thematic reversal of the seeing/perceiving failure in Isaiah.

In John 12:39, the inability to believe is explained as fulfillment of Isaiah's prophecy, directly citing the 'could not believe' from Isaiah 6.

In 2 Thessalonians 2:11, God sends a strong delusion to those who reject truth — the same divine hardening as here. People are made unable to understand.

Deuteronomy 29:4 says God withheld understanding—a direct parallel to the blindness Isaiah announces.

Mark 8:18 echoes Isaiah 6:9 directly, as Jesus asks the disciples if they have eyes that don't see and ears that don't hear.

Ezekiel 12:2 nearly quotes Isaiah 6:9, calling Israel a rebellious people with eyes that see not and ears that hear not.

Jeremiah 7:27 shows the prophet's message being rejected, just as Isaiah was told the people would not listen.

Jeremiah 6:10 describes uncircumcised ears unable to hear, mirroring the spiritual dullness of Isaiah's audience.

Jeremiah 5:21 uses the same 'eyes but do not see, ears but do not hear' imagery to describe Israel's stubbornness.

Mark 7:14 has Jesus calling everyone to listen and understand, opposing the failure to hear in Isaiah 6:9.

Matthew 15:10 has Jesus commanding the crowd to listen and understand, in direct contrast to the people's inability to hear in Isaiah.

Jeremiah 4:22 calls Israel foolish with no understanding, echoing the judgment of spiritual dullness in Isaiah 6:9.

Romans 11:8 echoes the spiritual blindness theme from Isaiah 6:9, citing a similar hardening passage.

In John 8:27, the Jews fail to understand Jesus' teaching about the Father, echoing the spiritual dullness of Isaiah's people.

In John 10:6, the listeners do not understand Jesus' parable, continuing the pattern of incomprehension from Isaiah's prophecy.

Job 33:14 says God speaks but man does not perceive it — echoing the 'hear but not understand' pattern in Isaiah 6:9.