Short answer
Yes. The Prophet ﷺ called Muharram the best month for voluntary fasting after Ramadan. In the Hanafi school fasting in Muharram is mustahabb (recommended), especially Ashura (the 10th) with the 9th or 11th. You may fast as many days as you like, but there is no required number. The four schools agree.
Fasting in Muharram is mustahabb, and Ashura is the most emphasised day in it. Fasting Ashura alone is makruh tanzihi, so join it with the 9th or the 11th.
The four schools agree on this.
Explanation
The Prophet ﷺ said that the best fasting after Ramadan is in Allah's month, Muharram, and the best prayer after the obligatory prayers is the prayer at night. Muharram is also one of the four sacred months, and the first month of the Hijri year.
How to fast in Muharram:
- Ashura (10th) with the 9th or the 11th. This is the most rewarded fast of the month. It expiates the sins of the year before. See fasting only the 10th.
- Any other days. Mondays and Thursdays, the white days (13th, 14th, 15th) or a run of days in the first ten nights are all good.
- The whole month. Allowed, but the Prophet ﷺ did not fast any whole month apart from Ramadan, so most scholars advise fasting much of it, not all of it.
What is not from the sunnah. There is no special fast for the 1st of Muharram or the Islamic New Year, and no authentic report about a fixed number of Muharram fasts with a set reward. Reports about special prayers on Ashura night are weak or fabricated.
If you owe Ramadan fasts, make them up first where you can. You may also fast your qada on these days, though a qada fast gives the reward of qada. For the date this year see Ashura and the Islamic New Year, and for the other voluntary fasts see the sunnah fasts.
The evidence
Quran, Surah At-Tawba 9:36
إِنَّ عِدَّةَ ٱلشُّهُورِ عِندَ ٱللَّهِ ٱثْنَا عَشَرَ شَهْرًۭا فِى كِتَٰبِ ٱللَّهِ يَوْمَ خَلَقَ ٱلسَّمَٰوَٰتِ وَٱلْأَرْضَ مِنْهَآ أَرْبَعَةٌ حُرُمٌۭ ۚ ذَٰلِكَ ٱلدِّينُ ٱلْقَيِّمُ ۚ فَلَا تَظْلِمُوا۟ فِيهِنَّ أَنفُسَكُمْ ۚ وَقَٰتِلُوا۟ ٱلْمُشْرِكِينَ كَآفَّةًۭ كَمَا يُقَٰتِلُونَكُمْ كَآفَّةًۭ ۚ وَٱعْلَمُوٓا۟ أَنَّ ٱللَّهَ مَعَ ٱلْمُتَّقِينَ ﴿٣٦﴾
Indeed, the number of months with Allah is twelve [lunar] months in the register of Allah [from] the day He created the heavens and the earth; of these, four are sacred. That is the correct religion, so do not wrong yourselves during them. And fight against the disbelievers collectively as they fight against you collectively. And know that Allah is with the righteous [who fear Him].
Muharram is one of the four sacred months.
Sahih Muslim 1163
Sahih... أفضل الصيام بعد رمضان شهر الله المحرم ...
"The best fasting after Ramadan is in Allah's month, Muharram."
Voluntary fasting in Muharram has special merit.
Sahih al-Bukhari 1969
Sahih... فما رأيت رسول الله صلى الله عليه وسلم استكمل صيام شهر إلا رمضان ...
"I never saw the Messenger of Allah fast a complete month except Ramadan."
The sunnah is to fast much of the month, not necessarily all of it.
Where the ruling is recorded
- al-Fatawa al-Hindiyya, Kitab al-Sawm, chapter on what is desirable and disliked in fasting. Fasting in Muharram is among the desirable fasts, and Ashura alone is disliked.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Sawm, before the chapter on what breaks the fast. Ashura is fasted with a day before or after.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.