Sunan Abi Dawud Fasting (Kitab Al-Siyam) Abu Ishaq al-Sabay'ai' أبو إسحاق السبيعي عمرو بن عبد الله Ibn Umm Maktum Muhammad bin 'Abdullah bin Numayr محمد بن عبد الله بن نمير Sulaiman bin Hayan al-Azdi سليمان بن حيان الأزدي Sahih That man and the people of his city should not fast as an atonement except that they know (for certain) that the people of a certain city of Muslims had fasted on Sunday. In that case they should keep fast as an atonement. https://parallelquran.com/hadith/sunan-abi-dawud-2333/