The Messenger of Allah ﷺ said, "The best fasting after Ramadan is in Allah's month of Muharram, and the best prayer after the obligatory prayers is the night prayer."
قال رسول الله ﷺ: أفضل الصيام بعد رمضان شهر الله المحرم، وأفضل الصلاة بعد الفريضة صلاة الليل.
Muslim narrated it in the Book of Fasting (1163), from Qutayba bin Saeed, who said, "Abu Awana narrated to us, from Abu Bishr, from Humayd bin Abdul-Rahman Al-Himyari, from Abu Hurairah," and he mentioned it.