Bara bin Azib reported,

During the time of the Prophet ﷺ, if a man was fasting and the time of breaking the fast arrived, but he fell asleep before eating, he was not allowed to eat that night nor the following day until evening came again.Qays bin Sirmah al-Ansari was fasting one day, and when the time of breaking the fast arrived, he came to his wife and asked, "Do you have any food?"She replied, "No, but let me go and find something for you."He had been working all day, and his eyes overcame him and he fell asleep. When his wife came back and saw him, she said, "What a disappointment for you."By midday the next day, he had fainted from exhaustion. This was mentioned to the Prophet ﷺ, and so this verse was revealed, "It has been made permissible for you on the night of fasting to approach your wives" [Baqarah 2:187]. They rejoiced greatly at this. Then was revealed, "And eat and drink until the white thread of dawn becomes distinct to you from the black thread" [Baqarah 2:187].

حدثنا عبد بن حميد حدثنا عبيد الله بن موسى عن إسرائيل بن يونس عن أبي إسحق

عن البراء قال

كان أصحاب النبي 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 هل عندك طعام قالت لا ولكن أنطلق فأطلب لك وكان يومه يعمل فغلبته عينه وجاءته 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} ففرحوا بها فرحا شديدا {وكلوا واشربوا حتى يتبين لكم الخيط الأبيض من الخيط الأسود من الفجر}