(31) باب التَّقَدُّمِ قَبْلَ شَهْرِ رَمَضَانَ
It was narrated from Abu Hurairah that the Messenger of Allah said:
"Do not fast ahead of the month, except for a man who habitually fasts, and that day happenes to be one of his regular fasts." '
Reference: Sunan an-Nasa'i 2172
In-book reference: Book 22, Hadith 83
English translation: Vol. 3, Book 22, Hadith 2174