חַטַּ֣את יְהוּדָ֗ה כְּתוּבָ֛ה בְּעֵ֥ט בַּרְזֶ֖ל בְּצִפֹּ֣רֶן שָׁמִ֑יר חֲרוּשָׁה֙ עַל־ל֣וּחַ לִבָּ֔ם וּלְקַרְנ֖וֹת מִזְבְּחוֹתֵיכֶֽם׃
O pecado de Judá está escrito com um ponteiro de ferro; com ponta de diamante está gravado na tábua do seu coração e nas pontas dos seus altares;
Rashi on Jeremiah
with a pen of iron This is an allegory. That is to say that it is deeply engraved, and cannot be erased. And the Midrash Aggadah explains: with a pen of iron, with a diamond point, preserved by Jeremiah, called ‘an iron wall,’ and by Ezekiel, to whom it was said (3:9): “As a diamond, harder than flint have I made your forehead.”
Rashi on Jeremiah
on the tablet of their heart that they do not forget their idolatry.