Narrated Al-Bara bin 'Azib:
"It was the custom among the Companions of Muhammad (ﷺ), that if any of them was fasting and the food was presented but he had slept before eating, he would not eat that night, nor the following day until the evening. Qais bin Sirmah Al-Ansari fasted and came to his wife at the time of Iftar, and said to her: 'No, but I will go and bring something for you.' He worked during the day, so his eyes (sleep) overcame him. Then his wife came, and when she saw him she said: 'You shall be disappointed.' About the middle of the next day he fainted. That was mentioned to the Prophet (ﷺ), so this Ayah was revealed: 'It is made lawful for you to have sexual relations with your women on the night of the fasts. So they were very happy about that. 'And eat and drink until the white thread (light) of dawn appears distinct to you from the black thread (of night). (2:187)'"
English reference: Vol. 5, Book 44, Hadith 2968
Arabic reference: Book 47, Hadith 3231