The Messenger of Allah ﷺ said, "Do not anticipate the month with fasting, except for a man who has a regular fast that happens to fall on that day."
أخبرنا إسحق بن إبراهيم قال أنبأنا الوليد عن الأوزاعي عن يحيى عن أبي سلمة
عن رسول الله ﷺ قال لا تقدموا قبل الشهر بصيام إلا رجل كان يصوم صياما أتى ذلك اليوم على صيامه
Bukhari reported it in the Book of Fasting, Chapter: Ramadan should not be preceded by fasting a day or two, hadith no. 1914, and Muslim reported it in the Book of Fasting, Chapter: Do not precede Ramadan by fasting a day or two, hadith no. 1082, from the hadith of Yahya bin Abu Kathir with this chain. It is also found in Sunan al-Kubra, hadith no. 2482. See the following hadith.Walid is Ibn Muslim.