[Machine] The Messenger of Allah ﷺ taught me prayer and fasting, and he said, "Pray like this and pray like that, and fast like this. When the sun sets, eat and drink until the white thread becomes distinct from the black thread of dawn, and fast for thirty days unless you see the crescent moon before that." So I took two threads, one black and one white from my hair, and I used to look at them but could not distinguish between them. So I mentioned that to the Messenger of Allah ﷺ , and he laughed and said, "O son of Hatim, that is just the whiteness of the day contrasting with the darkness of the night."  

عَلَّمَنِي رَسُولُ اللهِ ﷺ الصَّلَاةَ وَالصِّيَامَ فَقَالَ «صَلِّ كَذَا وَصَلِّ كَذَا وَصُمْ كَذَا فَإِذَا غَابَتِ الشَّمْسُ فَكُلْ وَاشْرَبْ حَتَّى يَتَبَيَّنَ لَكَ الْخَيْطُ الْأَبْيَضُ مِنَ الْخَيْطِ الْأَسْوَدِ مِنَ الْفَجْرِ وَصُمْ ثَلَاثِينَ يَوْمًا إلَّا أَنْ تَرَى الْهِلَالَ قَبْلَ ذَلِكَ» فَأَخَذْتُ خَيْطَيْنِ مِنْ شَعْرٍ أسْوَدَ وَأَبْيَضَ فَكُنْتُ أُبْصِرُ فِيهِمَا فَلَا يَتَبَيَّنُ لِي فَذَكَرْتُ ذَلِكَ لِرَسُولِ اللهِ ﷺ فَضَحِكَ فَقَالَ «يَا ابْنَ حَاتِمٍ إِنَّمَا ذَلِكَ بَيَاضُ النَّهَارِ مِنْ سَوَادِ اللَّيْلِ»