وَاشْتَعَلَ الرَّأْسُ شَيْبًا
And the head has flared with greyness.
Al-raʾs is the subject of ishtaʿala; shayban is an accusative specification (tamyīz) clarifying what the apparent “flare” consists of. Syntax itself directs the hearer away from literal flames.
The tamyīz and the image work together. Treating shayban as a direct object would obscure the clause’s grammatical structure and its figurative interpretation.