Musnad Ahmad 303:5

Muhammad ibn Ja'far narrated to us, Sa'id narrated to us, from Qatadah, from Mutarrif ibn 'Abdullah ibn al-Shikhkhir, from his father, that he heard the Prophet, peace and blessings of Allah be upon him, when he was asked about a man who fasts forever. He said: "He has neither fasted nor broken his fast."