Musnad Ahmad 62:1

'Abd al-Samad and 'Affan narrated to us, they said: Thabit narrated to us—'Affan said: Ibn Zayd Abu Zayd—Hilal ibn Khabbab narrated to us, from 'Ikrimah ibn Khalid, he said: A chief from the chiefs of Quraysh narrated to me, my father narrated to me, that he heard from the mouth of the Messenger of Allah, peace and blessings of Allah be upon him: "Whoever fasts Ramadan, and Shawwal, and Wednesday, and Thursday, and Friday, shall enter Paradise."