Sunan al-Nasa'i The Book of Fasting Abdur Rahman bin 'Amr al-Awza'i عبد الرحمن بن عمرو أبو عمرو الأوزاعي al-Harith bin Atyh al-Basri الحارث بن عطية البصري Ata' bin Abi Rabah عطاء بن أبي رباح Hajb bin Sulaiman حاجب بن سليمان ibn Umar “The Messenger of Allah used to fast three days in the middle of every month, and he rarely did not fast on Friday.” https://parallelquran.com/hadith/sunan-al-nasai-2373/