(13) باب شَهَادَةِ رَجُلَيْنِ عَلَى رُؤْيَةِ هِلاَلِ شَوَّالٍ
Narrated Rib'i b. Hirash:
On the authority of a man from the Companions of the Prophet (ﷺ): People differed among themselves on the last day of Ramadan (about the appearance of the moon of Shawwal). Then two bedouins came and witnessed before the Prophet (ﷺ) swearing by Allah that they had sighted moon the previous evening. So the Messenger of Allah (ﷺ) commanded the people to break the fast. The narrator Khalaf has added in his version: "and that they should proceed to the place of prayer (for 'Id)".
Reference: Sunan Abi Dawud 2339
In-book reference: Book 14, Hadith 27
English translation: Book 13, Hadith 2332