Sayyiduna Abu Huraira (may Allah be pleased with him) narrates in a marfu’ form that it was asked from the Prophet (peace and blessings be upon him): Which prayer is the best after the obligatory prayers? Which fast is the best after the fast of Ramadan? So the Prophet (peace and blessings be upon him) said: “After the obligatory prayer, the best prayer is a person’s prayer in the last third of the night, and after the fast of Ramadan, the best fast is the fast of Allah’s month, Muharram.”
Hadith Referenceمسند اسحاق بن راهويه / كتاب الصوم / 410
Hadith Takhrij«مسلم ، كتاب الصيام ، باب فضل صوم المحرم ، رقم : 1163 . سنن ابوداود ، كتاب الصيام ، باب فى صول المحرم ، رقم : 2429 . سنن ترمذي ، رقم : 438 . سنن ابن ماجه ، رقم : 1742 . مسند احمد : 302/2 .»