Sunan Ibn Majah
1650
Sahih+3

It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said:‘Do not anticipate Ramadan by fasting one or two days before, except for a man who has a habitual pattern of fasting, in which case let him fast.”

SahihAl-Albani
SahihMuhammad Fouad Abd al-Baqi