Yahya related to me from Malik that he had heard that once in thetime of Uthman ibn Affan the new moon had been seen in the afternoonand Uthman did not break his fast until evening had come and the sunhad set.Yahya said that he had heard Malik say that some onewho sees the new moon of Ramadan when he is on his own should startthe fast and not break it if he knows that that day is part ofRamadan. He added, "Some one who sees the new moon of Shawwal when heis on his own does not break the fast, because people suspect thereliability of someone among them who breaks the fast. Such peopleshould say, when they sight the new moon, 'We have seen the new moon.'Whoever sees the new moon of Shawwal during the day should not breakhis fast but should continue fasting for the rest of that day. This isbecause it is really the new moon of the night that is coming ."Yahya said that he heard Malik say, "If people are fasting on theday of Fitr thinking that it is still Ramadan and then definiteevidence comes to them that the new moon of Ramadan had been seen oneday before they began to fast and that they are now into the thirty-first day, then they should break the fast on that day at whatevertime the news comes to them. However, they do not pray the id prayerif they hear the news after the sun has begun to decline."
USC-MSA web (English) reference: Book 18, Hadith 4
Arabic reference: Book 18, Hadith 636