The companions of Muhammad ﷺ used to observe this practice, if a man was fasting and the time to break the fast arrived, but he fell asleep before eating, he would not eat for the rest of that night or the following day until evening came again.Qays bin Sirmah Ansari was fasting, and when the time to break his fast came he went to his wife and asked her, "Do you have any food?"She replied, "No, but let me go out and find some for you."He had been working all day, so his eyes overcame him and he fell asleep. When his wife came back and saw him, she said, "What a loss for you!" By midday he had fainted from exhaustion.This was mentioned to the Prophet ﷺ, and then this verse was revealed, "It has been made lawful for you to approach your wives on the night of the fast" [Baqarah 2:187]. They rejoiced over it tremendously. And there was also revealed, "Eat and drink until the white thread becomes distinct to you from the black thread" [Baqarah 2:187].
كان أصحاب محمد ﷺ إذا كان الرجل. صائما فحضر الإفطار فنام قبل أن يفطر لم يأكل ليلته ولا يومه حتى يمسي. وإن قيس بن صرمة الأنصاري كان صائما، فلما حضر الإفطار أتى امرأته فقال لها: عندك طعام؟ قالت: لا، ولكن أنطلق فأطلب لك، وكان يومه يعمل فغلبته عيناه فجاءته، امرأته، فلما رأته قالت: خيبة لك! فلما انتصف النهار غشي عليه، فذكر ذلك للنبي ﷺ فنزلت هذه الآية: {أحل لكم ليلة الصيام الرفث إلى نسائكم} [سورة البقرة: ١٨٧] ففرحوا بها فرحا شديدا، ونزلت: {وكلوا واشربوا حتى يتبين لكم الخيط الأبيض من الخيط الأسود} [سورة البقرة: ١٨٧].