Al-Matalib al-'Aliyah 3749 — Surah al-Hashr

It is narrated from Abu al-Mutawakkil al-Naji (may Allah have mercy on him) that a man from among the Muslims passed by who had been travelling on foot while fasting continuously for three days and could find nothing with which to break his fast; he kept waking up fasting in this condition, until an Ansari Companion called Thabit bin Qays (may Allah be pleased with him) came to know of his condition. He said to his family: "Tonight I will bring a guest of mine with me. When you set out the food, let one of you go to the lamp on the pretext of fixing it and put it out; then move your hands over the food as though you were eating, but do not eat until our guest has eaten his fill." So when evening came he brought him, and the family served the food; his wife got up on the pretext of fixing the lamp and put it out. Then they all moved their hands over the food as though they were eating, but they were not eating, until their guest had eaten his fill, while all their food was only a single loaf of bread, which was their own sustenance. When morning came, Sayyiduna Thabit (may Allah be pleased with him) came to the Messenger of Allah (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) said: "O Thabit! Allah Almighty was indeed very pleased with (marvelled at) you and this conduct of yours last night." The narrator says: Then this verse was revealed concerning them: "And they give (others) preference over themselves, even though they themselves are in severe hardship and want" [Surah al-Hashr: 9].
In the chain of this hadith, Isma'il bin Muslim al-Makki is weak; however, the origin of this story is narrated in Sahih al-Bukhari and Sahih Muslim from Sayyiduna Abu Hurayrah (may Allah be pleased with him), in which the event is attributed to an unnamed Ansari Companion.