Umm al-Darda' (may Allah be pleased with her) says that Abu al-Darda' (may Allah be pleased with him) would come after the morning had begun and say: Do you have any food? If he did not find any, he would say: I am fasting.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 7919