Sahih al-Bukhari 4509
Narrated Ash-Shu`bi:
`Adi took a white rope (or thread) and a black one, and when some part of the night had passed, he 
looked at them but he could not distinguish one from the other. The next morning he said, "O Allah's 
Apostle! I put (a white thread and a black thread) underneath my pillow." The Prophet (ﷺ) said, "Then 
your pillow is too wide if the white thread (of dawn) and the black thread (of the night) are underneath 
your pillow! "
حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ حُصَيْنٍ، عَنِ الشَّعْبِيِّ، عَنْ عَدِيٍّ، قَالَ أَخَذَ عَدِيٌّ عِقَالاً أَبْيَضَ وَعِقَالاً أَسْوَدَ حَتَّى كَانَ بَعْضُ اللَّيْلِ نَظَرَ فَلَمْ يَسْتَبِينَا، فَلَمَّا أَصْبَحَ قَالَ يَا رَسُولَ اللَّهِ، جَعَلْتُ تَحْتَ وِسَادَتِي‏.‏ قَالَ ‏
"‏ إِنَّ وِسَادَكَ إِذًا لَعَرِيضٌ أَنْ كَانَ الْخَيْطُ الأَبْيَضُ وَالأَسْوَدُ تَحْتَ وِسَادَتِكَ ‏"‏‏.‏