Jeremiah 2:22 compares unremovable sin to a stain that no washing can clean, paralleling the impossibility of changing one's nature.

Jeremiah 5:3 describes a people with harder-than-rock faces who refuse to repent, matching the inability to do good.

Jeremiah 6:29 depicts futile refining because wickedness is not removed, paralleling being accustomed to evil and unable to change.

In Jeremiah 9:5, the prophet likewise describes people who have taught their tongues to lie — habitual sin ingrained in their nature.

Jeremiah 17:9 calls the heart desperately sick and deceitful, directly paralleling the inability to do good from a corrupt nature.

In Jeremiah 38:7, an Ethiopian (Cushite) actually does good by rescuing Jeremiah — a counterpoint to the metaphor of an Ethiopian not changing his skin.

Jeremiah 6:30 declares them rejected silver, the consequence of failed refining—linking to incurable evil.

Mark 10:25 uses the same hyperbolic impossibility — a camel through a needle — to underscore human inability to save oneself.

John 6:44 reinforces the same principle: no one can come to Christ unless drawn by the Father — human inability requires divine enablement.

Acts 8:27 introduces an Ethiopian who, contrary to the proverb, is transformed through the gospel — heart change despite skin color.

Romans 8:7 explains why the leopard can't change its spots: the sinful mind is hostile to God and cannot submit to His law.

1 John 2:29 offers the solution: doing righteousness is possible only through being born of God — new birth enables what seemed impossible.

2 Peter 2:14 describes false teachers who cannot cease from sin — a parallel to the habitual evil that cannot be changed.

In 2 Kings 17:40, the Samaritans persisted in their former practices — illustrating the same stubborn adherence to evil despite warnings.

In Isaiah 1:5, the same theme of Israel's persistent rebellion despite punishment appears — they cannot stop sinning.