حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ إِدْرِيسَ، عَنْ حُصَيْنٍ، عَنِ الشَّعْبِيِّ، عَنْ عَدِيِّ بْنِ حَاتِمٍ، - رضى الله عنه - قَالَ لَمَّا نَزَلَتْ ‏{‏ حَتَّى يَتَبَيَّنَ لَكُمُ الْخَيْطُ الأَبْيَضُ مِنَ الْخَيْطِ الأَسْوَدِ مِنَ الْفَجْرِ‏}‏ قَالَ لَهُ عَدِيُّ بْنُ حَاتِمٍ يَا رَسُولَ اللَّهِ إِنِّي أَجْعَلُ تَحْتَ وِسَادَتِي عِقَالَيْنِ عِقَالاً أَبْيَضَ وَعِقَالاً أَسْوَدَ أَعْرِفُ اللَّيْلَ مِنَ النَّهَارِ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ إِنَّ وِسَادَتَكَ لَعَرِيضٌ إِنَّمَا هُوَ سَوَادُ اللَّيْلِ وَبَيَاضُ النَّهَارِ ‏"‏ ‏.‏

'Adi b. Hatim (Allah be pleased with him) reported that when (this verse) was revealed: " Until the white streak of the dawn becomes distinct from the dark streak" (ii. 187) Adi b. Hatim said: Messenger of Allah, verily I keep underneath my pillow two strings, one white and the other black, by which I distinguish night from dawn. Upon this the Messenger of Allah (PBUH) said: Your pillow seems to be very large. For the word khait implies the blackness of the night and the whiteness of the dawn. Translation Not Available

Book Ref: Sahih Muslim Book 13 Hadith 2396
Web Ref:  Sahih Muslim Book 6 Hadith 1090