Muharram is one of the sacred months of the year. Fasting this month is highly recommended.
Abu Hurayrah narrated that the Prophet (Sallallaahu alayhi wa sallam) said:
“The best fasting after the month of Ramadaan is the month of Allaah, the Muharram” [Saheeh Muslim]
Allaah's Messenger called this month the month of Allaah and as we know that when this type of idaafah is
mentioned and it is related to the name of Allaah, then it means that object has greatness, honor and deserves our
respect and veneration as is prescribed in the shariah. Like baytullah, naaqatullaah, rosuulullaah….
So, we understand the great importance of this month, however fasting in this month shouldn't be done as a whole
as we know from the sunnah that the Prophet (saw) never fasted a full whole month except the month of
Ramadaan. So, what the hadith in saheeh Muslims means is to fast a lot of days in Muharram – but not the whole
month and Allaah knows best.