Mishkat al-Masabih 29 Excellent Qualities and Description of the Prophet كتاب الفضائل والشمائل 103

وَعَنْ عُبَادَةَ بْنِ الصَّامِتِ قَالَ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذا نزل عَلَيْهِ الْوَحْيُ كُرِبَ لِذَلِكَ وَتَرَبَّدَ وَجْهُهُ. وَفِي رِوَايَة: نكَّسَ رأسَه ونكَّسَ أصحابُه رؤوسَهم فَلَمَّا أُتْلِيَ عَنْهُ رَفَعَ رَأْسَهُ. رَوَاهُ مُسْلِمٌ

`Ubada b. as-Samit said that when the inspiration descended on the Prophet, he was distressed on account of that and his face was altered to a dark hue. A version says, he lowered his head and his companions lowered their heads; then when it was removed from him, he raised his head. Muslim transmitted it.