The Prophet ﷺ said, "Do not precede the fast of Ramadan by a day or two, unless it is a fast that a man regularly observes, in which case let him observe that fast."
حدثنا مسلم بن إبراهيم حدثنا هشام عن يحيى بن أبي كثير عن أبي سلمة
عن النبي ﷺ قال لا تقدموا صوم رمضان بيوم ولا يومين إلا أن يكون صوم يصومه رجل فليصم ذلك الصوم
Bukhari narrated it in the Book of Fasting, Chapter: One should not anticipate Ramadan by fasting a day or two before it, hadith no. 1914, and Muslim in the Book of Fasting, Chapter: Do not anticipate Ramadan by fasting a day or two before it, hadith no. 1082, from the hadith of Hisham with the same chain.