ישעיהו, פרק מ״ח, פסוק ד׳

A stark diagnosis of spiritual stubbornness reveals how deeply rooted human resistance to divine truth can become. Through vivid physical imagery, a profound state of mental and spiritual blockage is exposed. God addresses the unbelieving descendants of Jacob out of a deep familiarity with their nature [רש״י, ביאור שטיינזלץ], making it clear that He is already intimately aware of their hardened hearts [אבן עזרא, מצודת דוד]. The primary approach among commentators is that this prior knowledge explains exactly why God had to announce His miracles well in advance. If a miraculous event occurred suddenly and without warning, the people would naturally attribute it to their idols [רש״י] or simply fail to recognize it as divine intervention at all [מלבי״ם]. Even though God knows they have a history of ignoring past salvations, He continues to offer them guidance and correction [רד״ק].

The people suffer from a deep internal stubbornness, making it incredibly difficult to soften them or persuade them with moral instruction [ביאור שטיינזלץ]. They possess an inherent emotional block toward faith [מלבי״ם]. This resistance is illustrated by comparing the back of their neck [מצודת ציון] and the muscles responsible for movement [שד״ל] to a solid, jointless iron rod [מצודת ציון, מצודת דוד, רד״ק]. Having turned their backs on God, they refuse to abandon their destructive paths [אבן עזרא]. Their stiffness is so severe that they are seemingly incapable of turning their heads back to look toward God [מצודת דוד, רד״ק] or even to notice the clear miracles unfolding right around them [מלבי״ם].

Completing this picture of defiance is the image of a forehead made of copper [מצודת ציון, ביאור שטיינזלץ]. Because the face is where feelings of shame or boldness are most visible, a copper forehead represents extreme arrogance. It describes someone who confronts those trying to correct him with total disrespect, completely lacking any sense of shame or embarrassment [רד״ק, מצודת דוד, שד״ל, אבן עזרא]. Ultimately, this profound arrogance is what allows the people to stare directly at divine wonders, yet still boldly deny the very reality they see with their own eyes [מלבי״ם].