he asked the Messenger of Allah about the verse "Until the white thread (light) of dawn appears to you distinct from the black thread (darkness of night)." He said: "It is the blackness of the night and the whiteness of the day." '  

أَنَّهُ سَأَلَ رَسُولَ اللَّهِ ﷺ عَنْ قَوْلِهِ تَعَالَى { حَتَّى يَتَبَيَّنَ لَكُمُ الْخَيْطُ الأَبْيَضُ مِنَ الْخَيْطِ الأَسْوَدِ } قَالَ هُوَ سَوَادُ اللَّيْلِ وَبَيَاضُ النَّهَارِ  

"When 'Until the white (light) thread of dawn appears distinct to you from the black thread (of night)' was revealed, the Prophet ﷺ said to me: 'That only refers to the whiteness of the day from the blackness of the night.'" (Using translation from Tirmidhī 2970)   

لَمَّا نَزَلَتْ {وَكُلُوا وَاشْرَبُوا حَتَّى يَتَبَيَّنَ لَكُمُ الْخَيْطُ الْأَبْيَضُ مِنَ الْخَيْطِ الْأَسْوَدِ} قَالَ النَّبِيُّ ﷺ «إِنَّمَا ذَلِكَ بَيَاضُ النَّهَارِ وَسَوَادُ اللَّيْلِ»  

("الخَيطُ الأبْيَضُ منَ الخَيط الأسْوَد من الفَجْرِ انمَّا هُمَا سَوادُ اللَّيل وبياضُ النَّهار".