Sayyiduna Bara’ bin Azib (may Allah be pleased with them both) said: In the early days of Islam, when the companions of the Messenger of Allah (peace and blessings be upon him) were fasting and the time for breaking the fast came, if any fasting person slept before breaking his fast, then he could not eat that night nor the following day until evening. Then it happened that Sayyiduna Qais bin Sirmah Al-Ansari (may Allah be pleased with him) was fasting. When the time for breaking the fast came, he went to his wife and said: “Do you have anything to eat?” She said: “At this moment, there is nothing, but I will go and bring something.” Qais had worked all day, so he fell asleep. When his wife returned, she saw him sleeping and said: “Alas, you have been deprived.” When it was midday, Qais fainted. When this was mentioned to the Prophet (peace and blessings be upon him), this verse was revealed: «أُحِلَّلَكُمْلَيْلَةَالصِّيَامِالرَّفَثُإِلَىنِسَائِكُمْ ......»[بقره: 187/2] meaning: “It has been made lawful for you to go to your wives on the nights of fasting.” Upon this, the companions (may Allah be pleased with them) were very happy and they ate and drank until the white thread (of dawn) became distinct to them from the black thread.
By the black thread is meant the false dawn, which is the darkness of the night, and by the white thread is meant the true dawn and the light of the morning. In the early days of Islam, people would eat, drink, and have relations with their wives after breaking the fast, but after sleeping, they could not do any of these things until the time for breaking the fast arrived again.
However, later Allah Ta‘ala informed (the believers) of the details regarding fasting, and the aforementioned noble verse was revealed, and all the previous difficulties were made easy. Then the people found peace and comfort.