From Sahih Muslim (Hadith 2718):
Abdullah b. Shaqiq reported:I said to 'A'isha (Allah be pleased with her): Did the Messenger of Allah (ﷺ) observe fast during a month? She said, I do not know of any month in which he fasted throughout except Ramadan and (the month) in which he did not fast at all till he ran the course of his life. May peace be upon him
Reference: Muslim 2718