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