The Messenger of Allah ﷺ said, "Abu Dharr, when you fast three days of the month, fast the thirteenth, the fourteenth, and the fifteenth."
حدثنا محمود بن غيلان حدثنا أبو داود قال أنبأنا شعبة عن الأعمش قال سمعت يحيى بن سام يحدث عن موسى بن طلحة قال سمعت
قال رسول الله ﷺ يا أبا ذر إذا صمت من الشهر ثلاثة أيام فصم ثلاث عشرة وأربع عشرة وخمس عشرة
[Its isnad is hasan]. Nasai also narrated it: 4/222, no. 2425 (Fasting, mention of the disagreement over Musa bin Talha in the report, etc.) through the hadith of Shuba, with this wording. It is also in Musnad Tayalisi, no. 475. Ibn Khuzayma graded it sahih: 3/302-303, no. 2128, as did Ibn Hibban, no. 943, 944.On this subject there are also narrations from Abu Qatada [Muslim, no. 1162], Abdullah bin Amr [Bukhari, no. 1131, and Muslim, 1159], Qurra bin Iyas Muzani [Ahmad 3/435, 436], Abdullah bin Masud [mentioned earlier, no. 742], Abu Uqrub [Nasai, no. 435, and Ahmad, 447], Ibn Abbas [Nasai, no. 2347], Ayesha [coming later, no. 763], Qatada bin Milhan [Abu Dawud, no. 2449, and Ibn Majah, no. 1707], Uthman bin Abu As [Nasai, no. 2413], and Jareer [Nasai, no. 2422].