Sunan an-Nasa'i, Volume 3, Book 22, Hadith 2171 (DarusSalam) ⓘ
It was narrated from 'Adiyy bin Hatim that: 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." '
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ حَدَّثَنَا جَرِيرٌ، عَنْ مُطَرِّفٍ، عَنِ الشَّعْبِيِّ، عَنْ عَدِيِّ بْنِ حَاتِمٍ، أَنَّهُ سَأَلَ رَسُولَ اللَّهِ صلى الله عليه وسلم عَنْ قَوْلِهِ تَعَالَى { حَتَّى يَتَبَيَّنَ لَكُمُ الْخَيْطُ الأَبْيَضُ مِنَ الْخَيْطِ الأَسْوَدِ } قَالَ " هُوَ سَوَادُ اللَّيْلِ وَبَيَاضُ النَّهَارِ " .
also referenced under: Hadith 2169 (Reference) & Book 22, Hadith 80 (In-Book)