Musnad Ahmad 30:2606

Waki’ and ‘Abd al-Rahman narrated to us, from Sufyan, from Abu al-Zinad, from Musa ibn Abi ‘Uthman, from his father, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "A woman shall not fast a single day while her husband is present, except with his permission." Waki’ said: Except for Ramadan.