Hadith 8:345
Abu Bakr narrated to us, he said: Hafs bin Ghiyath narrated to us, from Layth, from Tawus and Ata, they both said: "He does not fast the three [days] except in the ten [days of Dhu al-Hijjah]." And Mujahid said: "There is no harm in fasting them during the months of Hajj."
حدثنا أبو بكر قال ثنا حفص بن غياث عن ليث عن طاوس وعطاء قالا لا يصوم الثلاثة إلا في العشر وقال مجاهد لا بأس أن يصومها في أشهر الحج