Concerning a man who lived in one of the cities and fasted on Monday, while two men testified that they had sighted the crescent moon on Sunday night, he said that neither this man nor the people of his city are required to make up that day, unless they come to know that the people of one of the Muslim cities had fasted on Sunday, in which case they must make it up.
حدثنا عبيد الله بن معاذ حدثني أبي
في رجل كان بمصر من الأمصار فصام يوم الاثنين وشهد رجلان أنهما رأيا الهلال ليلة الأحد فقال لا يقضي ذلك اليوم الرجل ولا أهل مصره إلا أن يعلموا أن أهل مصر من أمصار المسلمين قد صاموا يوم الأحد فيقضونه
No references are available.
Its chain of transmission is sahih. Abu Bakr Jassas transmitted it in Ahkam al-Quran: 1/276, through the hadith of Abu Dawud, with the same chain.Ashath is Ibn Abdullah bin Jabir.