It wasnarrated that Abu Hurairah said:
"The Messenger of Allah (ﷺ)forbade anticipating the fast by fasting one day before sighting (ofthe crescent)." (JA)
English reference (JA): Vol. 1, Book 7, Hadith 1646 (JA)
Arabic reference (JA): Book 7, Hadith 1715 (JA)