Sunan Abi Dawud Fasting (Kitab Al-Siyam) al-Hur bin al-Sabah الحر بن الصباح النخعي Hunayda bin Khalid Masdad bin Masrhad مسدد بن مسرهد بن مسربل Wadah bin 'Abdullah al-Yashkari وضاح بن عبد الله اليشكري أبو عوانة Sahih The client of Usamah ibn Zayd said that he went along with Usamah to Wadi al-Qura in pursuit of his camels. He would fast on Monday and Thursday. His client said to him: Why do you fast on Monday and Thursday, while you are an old man? He said: The Prophet of Allah (ﷺ) used to fast on Monday and Thursday. When he was asked about it, he said: The works of the servants (of Allah) are presented (to Allah) on Monday and Thursday. https://parallelquran.com/hadith/sunan-abi-dawud-2436/