Musannaf Ibn Abi Shayba 7:431

Al-Thaqafi narrated to us, from Khalid al-Hadhdha’, who said: ‘Asim said: I asked Jabir ibn Zayd (Abu al-Sha’tha’) and said: “Has it reached you regarding one who breaks his fast for a day of Ramadan, what is upon him?” He said: “No, but he should fast a day in its place and perform an act of kindness for that.”