When the above verses were revealed: 'Until the white thread appears to you, distinct from the black thread,' I took two (hair) strings, one black and the other white, and kept them under my pillow and went on looking at them throughout the night but could not make anything out of it. So, the next morning I went to Messenger of Allah ﷺ and told him the whole story. He explained to me, "That verse means the darkness of the night and the whiteness of the dawn."  

لَمَّا نَزَلَتْ {حَتَّى يَتَبَيَّنَ لَكُمُ الْخَيْطُ الأَبْيَضُ مِنَ الْخَيْطِ الأَسْوَدِ} عَمَدْتُ إِلَى عِقَالٍ أَسْوَدَ وَإِلَى عِقَالٍ أَبْيَضَ فَجَعَلْتُهُمَا تَحْتَ وِسَادَتِي فَجَعَلْتُ أَنْظُرُ فِي اللَّيْلِ فَلاَ يَسْتَبِينُ لِي فَغَدَوْتُ عَلَى رَسُولِ اللَّهِ ﷺ فَذَكَرْتُ لَهُ ذَلِكَ فَقَالَ إِنَّمَا ذَلِكَ سَوَادُ اللَّيْلِ وَبَيَاضُ النَّهَارِ  

" 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 ﷺ said: Your pillow seems to be very large. For the word khait implies the blackness of the night and the whiteness of the dawn.  

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 ﷺ إِنَّ وِسَادَتَكَ لَعَرِيضٌ إِنَّمَا هُوَ سَوَادُ اللَّيْلِ وَبَيَاضُ النَّهَارِ  

When the verse "Until the white thread of dawn appear to you distinct from its black thread" was revealed, I took a white rope and a black rope, and placed them beneath my pillow ; and then I looked at them, byt they were not clear to me. So I mentioned it to the Messenger of Allah ﷺ. He laughed and said: Your pillow is so broad and lengthy ; that is (i.e. means) night and day. The version of the narrator 'Uthman has: That is the blackness of night and whiteness of day.  

لَمَّا نَزَلَتْ هَذِهِ الآيَةُ { حَتَّى يَتَبَيَّنَ لَكُمُ الْخَيْطُ الأَبْيَضُ مِنَ الْخَيْطِ الأَسْوَدِ } قَالَ أَخَذْتُ عِقَالاً أَبْيَضَ وَعِقَالاً أَسْوَدَ فَوَضَعْتُهُمَا تَحْتَ وِسَادَتِي فَنَظَرْتُ فَلَمْ أَتَبَيَّنْ فَذَكَرْتُ ذَلِكَ لِرَسُولِ اللَّهِ ﷺ فَضَحِكَ فَقَالَ إِنَّ وِسَادَكَ لَعَرِيضٌ طَوِيلٌ إِنَّمَا هُوَ اللَّيْلُ وَالنَّهَارُ قَالَ عُثْمَانُ إِنَّمَا هُوَ سَوَادُ اللَّيْلِ وَبَيَاضُ النَّهَارِ  

[Machine] When this verse was revealed: "And eat and drink until the white thread of dawn becomes distinct to you from the black thread (of night)" (Quran 2:187), I intended to distinguish between two headbands, one black and the other white. So I placed them under my pillow and looked at them, but I couldn't differentiate between the white and the black. When I woke up in the morning, I went to the Messenger of Allah ﷺ and informed him about what I had done. He said, "That is the whiteness of the day and the darkness of the night."  

لَمَّا نَزَلَتْ هَذِهِ الْآيَةُ {وَكُلُوا وَاشْرَبُوا حَتَّى يَتَبَيَّنَ لَكُمُ الْخَيْطُ الْأَبْيَضُ} [البقرة 187] مِنَ الْخَيْطِ الْأَسْوَدِ قَالَ عَمَدْتُ إِلَى عِقَالَيْنِ أَحَدُهُمَا أَسْوَدُ وَالْآخَرُ أَبْيَضُ فَجَعَلْتُهُمَا تَحْتَ وِسَادِي قَالَ ثُمَّ جَعَلْتُ أَنْظُرُ إِلَيْهِمَا فَلَا تُبِينُ لِي الْأَسْوَدَ مِنَ الْأَبْيَضِ وَلَا الْأَبْيَضَ مِنَ الْأَسْوَدِ فَلَمَّا أَصْبَحْتُ غَدَوْتُ عَلَى رَسُولِ اللهِ ﷺ فَأَخْبَرْتُهُ بِالَّذِي صَنَعْتُ فَقَالَ إِنْ كَانَ وِسَادُكَ إِذًا لَعَرِيضًا إِنَّمَا ذَلِكَ بَيَاضُ النَّهَارِ مِنْ سَوَادِ اللَّيْلِ  

When the verse "Until the white thread of dawn appear to you distinct from its black thread" was revealed, I took a white rope and a black rope, and placed them beneath my pillow ; and then I looked at them, byt they were not clear to me. So I mentioned it to the Messenger of Allah ﷺ. He laughed and said: Your pillow is so broad and lengthy ; that is (i.e. means) night and day. The version of the narrator 'Uthman has: That is the blackness of night and whiteness of day. (Using translation from Abū Dāʾūd 2349)   

لَمَّا نَزَلَتْ هَذِهِ الْآيَةُ {حَتَّى يَتَبَيَّنَ لَكُمُ الْخَيْطُ الْأَبْيَضُ} مِنَ الْخَيْطِ الْأَسْوَدِ أَخَذْتُ عِقَالًا أَبْيَضَ وَعِقَالًا أَسْوَدَ فَوَضَعْتُهَا تَحْتَ وِسَادَتِي فَنَظَرْتُ فَلَمْ أَتَبَيَّنْ فَذَكَرْتُ ذَلِكَ لِلنَّبِيِّ ﷺ فَضَحِكَ وَقَالَ «إِنَّ وِسَادَكَ إِذًا لَعَرِيضٌ طَوِيلٌ إِنَّمَا هُوَ اللَّيْلُ»