In biblical literature, the imagery of an iron stylus and a diamond point is used to convey themes of permanence, indelibility, and the hardness of the human heart. These metaphors are found in the prophetic writings of the Old Testament, particularly in the book of Jeremiah.

Jeremiah 17:1 :
"The sin of Judah is written with an iron stylus, with a diamond point it is engraved on the tablet of their hearts and on the horns of their altars."

In this passage, the prophet Jeremiah uses the metaphor of an iron stylus with a diamond point to describe the deep-seated and enduring nature of Judah's sin. The iron stylus, a tool used for engraving, symbolizes the act of inscribing something permanently. The diamond point, known for its hardness, emphasizes the unyielding and stubborn nature of the people's sinfulness. This imagery suggests that the sin of Judah is not superficial or easily erased but is deeply embedded in their hearts and practices.

The use of an iron stylus and diamond point in this context highlights the severity of Judah's spiritual condition. The heart, often seen as the center of will and emotion in biblical anthropology, is depicted as a tablet upon which sin is permanently inscribed. This metaphor underscores the idea that the people's rebellion against God is not merely a matter of external actions but is rooted in their innermost being.

The reference to the "horns of their altars" further illustrates the pervasive nature of their sin. The horns of the altar were considered sacred, representing strength and refuge. By stating that sin is engraved on these horns, Jeremiah indicates that even their places of worship have been corrupted by their iniquity.

The imagery of the iron stylus and diamond point serves as a powerful indictment of the people's hardened hearts and their persistent disobedience to God's covenant. It calls the audience to recognize the depth of their sin and the need for genuine repentance and transformation.

In the broader biblical narrative, this metaphor aligns with the recurring theme of the hardness of the human heart and the need for divine intervention to bring about true change. The prophets often spoke of a future time when God would give His people a new heart and write His law upon it, as seen in passages like Ezekiel 36:26 and Jeremiah 31:33. This promise of a new covenant points to the hope of redemption and restoration through God's grace and the transformative work of the Holy Spirit.