A severe double warning addresses the dangers of unchecked pride and arrogance, cautioning against both an attitude of superiority and the defiant speech that follows it [רד״ק, מלבי״ם]. The primary approach among commentators views this as a call to avoid looking down on others or harboring an inflated sense of personal triumph. Pride often develops in stages. A person might first assert dominance over their peers and equals. If left unchecked, however, this arrogance swells until the individual ultimately rebels against God Himself [אבן עזרא].
Taking a different approach, the upward focus of this pride can be understood as a reference to the heavenly spheres and constellations. In this light, the warning cautions against attributing one's success and power to astrology or the stars. Relying on the influence of celestial bodies is a dangerous mindset that ultimately leads to the denial of God's direct involvement and guidance in the world [אלשיך].
This deep-seated pride inevitably spills over into action, resulting in harsh and forceful speech directed against God [רד״ק, אלשיך]. The imagery used to describe this rebellion is that of a person speaking with an uplifted neck, a universal posture of intense arrogance [מצודת דוד, ביאור שטיינזלץ]. Some commentators link this stiff posture to physical fatness and material excess. It pictures an individual who has grown thick and strong from experiencing too much wealth, abundance, and material success. Sated by endless comfort, the person speaks with superiority and denies God [רד״ק, מאירי, אלשיך]. Ultimately, this concept of immense strength and thickness can characterize either the harsh words pouring from the person's mouth or the sheer physical stubbornness of the proud neck itself [אבן עזרא].