In Acts 3:19, Peter calls for repentance and turning to blot out sins — the very turning that Acts 28:27 says the people refuse.

In Exodus 8:32, Pharaoh hardens his heart — a pattern of willful refusal that parallels the dullness of heart described here.

In Deuteronomy 29:4, this same lack of spiritual understanding is attributed to God not granting it—a direct parallel to the dull hearts here.

Psalm 17:10 uses the same 'fat heart' imagery for those who close themselves to pity, echoing the dull hearts that refuse to turn.

Psalm 119:70 also describes a 'fat heart' insensitive to God's law, reinforcing the same stubborn resistance seen in Acts.

Isaiah 6:9 is the source of the quote in Acts—the command to proclaim to a people who hear but do not understand.

Isaiah 6:10 is the direct source of the quote—God hardening the heart so they cannot turn and be healed.

In Isaiah 29:10, God pours out a spirit of deep sleep, closing eyes — the same divine hardening echoed in Paul's quotation of Isaiah 6.

In Ezekiel 12:2, God describes Israel as having eyes to see but not seeing — almost identical language to the calloused hearts in Acts 28:27.

In Zechariah 7:12, the people make their hearts like stone to avoid hearing — directly parallel to the calloused hearts and closed eyes here.

In Mark 8:18, Jesus rebukes the disciples with 'having eyes do you not see?' — the same charge of spiritual dullness, applied even to insiders.

In Luke 8:10, Jesus quotes Isaiah 6:9–10, the same source as Paul's citation — showing the pattern of parables hiding truth from the hardened.

In 2 Corinthians 3:14, Paul says the minds of Israel are hardened with a veil — the same callousness as the heart grown dull in Acts 28:27.

Hebrews 5:11 echoes the same 'dull of hearing' condition — the audience is slow to learn, matching the hardened hearts here.

Psalm 69:23 asks for darkened eyes as a curse—a judgment that mirrors the closed eyes preventing understanding and healing.