Musnad Ahmad 30:661

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from Yahya ibn Abi Kathir, from Abu Salamah, from Abu Hurayrah, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) forbade hastening the month of Ramadan by fasting a day or two before it, except for a man who used to fast a fast, so that [the day] coincides with his fasting."