Allah’s sacred month of Muharram is a blessed and important month.

It is the first month of the Hijri calendar and is one of the four sacred months concerning which Allah says: “Verily, the number of months with Allah is 12 months (in a year), so it was ordained by Allah on the Day when He created the heavens and the earth; of them, four are sacred. That is the right religion, so wrong not yourselves therein.” (Qur’an, 9:36)
Abu Bakr (may Allah be pleased with him) reported that the Prophet (peace and blessings of Allah be upon him) said: “The year is 12 months of which four are sacred, the three consecutive months of Dul Qadah, Dul Hijjah and Muharram, and Rajab, which comes between Jumada and Shaban.” (Bukhari)
Muharram is so called because it is a sacred (muharram) month and to confirm its sanctity. Allah Almighty says: “... so wrong not yourselves therein …” (Tafsir of Ibn Kathir)

Nafl fasts during Muharram
Abu Hurayrah (may Allah be pleased with him) said: “The Messenger of Allah (peace be upon him) said: ‘The best of fasting after Ramadan is fasting Allah’s month of Muharram.” (Muslim)

Ashura in history
Ibn Abbas said: “The Prophet (peace be upon him) came to Madinah and saw Jews fasting on Ashura. He said, ‘What is this?’ They said, ‘This is a righteous day, it is the day when Allah saved the Children of Israel from their enemies, so Musa fasted on this day.’ He said, ‘We have more right to Musa than you,’ so he fasted on that day and commanded (the Muslims) to fast on that day.” (Bukhari)
The practice of fasting on Ashura was known even in the days of Jahiliyyah, before the Prophet’s mission. It was reported that Ayesha (may Allah be pleased with her) said: “The people of Jahiliyyah used to fast on that day.” Apparently the motive for commanding the Muslims to fast on this day was the desire to be different from the Jews, so that the Muslims would fast when the Jews did not, because people do not fast on a day of celebration. (Bukhari)
Fasting on Ashura was a gradual step in the process of introducing fasting as a prescribed obligation in Islam. Fasting appeared in three forms. When the Messenger of Allah (peace be upon him) came to Madinah, he told the Muslims to fast on three days of every month and on the day of Ashura, then Allah made fasting obligatory when He said: “ … observing the fasting is prescribed for you … “ (Al-Qur’an, 2:183) The obligation was transferred from the fast of Ashura to the fast of Ramadan, and this is one of the proofs in the field of Usul Al-Fiqh that it is possible to abrogate a lighter duty in favor of a heavier duty.
Before the obligation of fasting Ashura was abrogated, fasting on this day was obligatory, as can be seen from the clear command to observe this fast. Then it was further confirmed later on, then reaffirmed by making it a general command addressed to everybody, and once again by instructing mothers not to breastfeed their infants during this fast. It was reported from Ibn Mas’ud that when fasting Ramadan was made obligatory, the obligation to fast Ashura was lifted i.e. it was no longer obligatory to fast on this day, but it is still desirable (mustahab).

Virtues of fasting on Ashura
Ibn Abbas said: “I never saw the Messenger of Allah (peace be upon him) so keen to fast any day and give it priority over any other than this day, the day of Ashura and this month (Ramadan). (Bukhari)
The Prophet (peace be upon him) said: “For fasting the day of Ashura, I hope that Allah will accept it as expiation for the year that went before.” (Muslim)
This is from the bounty of Allah toward us: For fasting one day He gives us expiation for the sins of a whole year. And Allah is the Owner of Great Bounty.

Which day is Ashura?
An-Nawawi said: “Ashura and Tasua are two elongated names (the vowels are elongated) as is stated in books on the Arabic language. Our companions said: Ashura is the 10th day of Muharram and Tasua is the 9th day. This is the opinion of the majority of scholars.” (Al-Majmua)

Common innovations on Ashura
Commenting on things that some people do on Ashura, such as wearing kohl, taking a bath (ghusl), wearing henna, shaking hands with one another, cooking grains (hubub), showing happiness and so on, Shaykh ul-Islam Ibn Taymiyyah said: “Nothing to that effect has been reported in any Sahih Hadith from the Prophet (peace be upon him) or from his companions. None of the Imams of the Muslims encouraged or recommended such things, neither the four Imams, nor any others. No reliable scholars have narrated anything like this, neither from the Prophet (peace be upon him), nor from the cpmpanions, nor from the Tabi’in; neither in any sahih report or in a dayeef (weak) report; neither in the books of Sahih, nor in As-Sunan, nor in the Musnads. No Hadith of this nature was known during the best centuries.
They also reported a fabricated Hadith that is falsely attributed to the Prophet (peace be upon him), which says, “Whoever is generous to his family on the day of Ashura, Allah will be generous to him for the rest of the year.” Reporting all of this from the Prophet (peace be upon him) is tantamount to lying.”

n Courtesy: sunnahonline.com



Then Ibn Taymiyyah discussed in brief the tribulations that had occurred in the early days of this Ummah and the killing of Al-Hussain (may Allah be pleased with him), and what the various sects had done because of this. Then he said:
“An ignorant, wrongful group, who was either heretics and hypocrites, or misguided and misled, made a show of allegiance to him and the members of his household, so they took the day of Ashura as a day of mourning and wailing, in which they openly displayed the rituals of jahiliyyah such as slapping their cheeks and rending their garments, grieving in the manner of the jahiliyyah and so on.
“The Shaytan made this attractive to those who are misled, so they took the day of Ashura as an occasion of mourning, when they grieve and wail, recite poems of grief and tell stories filled with lies. Whatever truth there may be in these stories serves no purpose other than the renewal of their grief and sectarian feeling, and the stirring up of hatred and hostility among the Muslims, which they do by cursing those who came before them
“The evil and harm that they do to the Muslims cannot be enumerated by any man, no matter how eloquent he is. Some others — either Nasibis who oppose and have enmity toward Al-Husayn and his family or ignorant people who try to fight evil with evil, corruption with corruption, lies with lies and bidah with bidah — opposed them by fabricating reports in favor of making the day of Ashura a day of celebration, by wearing kohl and henna, spending money on one’s children, cooking special dishes and other things that are done on Eid and special occasions. These people took the day of Ashura as a festival like Eid, whereas the others took it as a day of mourning. Both are wrong, and both go against the Sunnah, even though the other group (those who take it as a day of mourning) are worse in intention and more ignorant and more plainly wrong …
“Neither the Prophet (peace be upon him) nor his successors (the caliphs) did any of these things on the day of Ashura, they neither made it a day of mourning nor a day of celebration …
“As for the other things, such as cooking special dishes with or without grains, or wearing new clothes, or spending money on one’s family, or buying the year’s supplies on that day, or doing special acts of worship such as special prayers or deliberately slaughtering an animal on that day, or saving some of the meat of the sacrifice to cook with grains, or wearing kohl and henna, or taking a bath (ghusl), or shaking hands with one another, or visiting one another, or visiting the mosques and shrines and so on … all of this is reprehensible bid’ah and is wrong. None of it has anything to do with the Sunnah of the Messenger of Allah (peace and blessings of Allah be upon him) or the way of the Khulafa’ ar-Rashidun. It was not approved of by any of the Imams of the Muslims, not Malik, not ath-Thawri, not Al-Layth ibn Sa’ad, not Abu Hanifah, not Al-Awza’i, not Al-Shafi’i, not Ahmad ibn Hanbal, not Ishaq ibn Rahwayh, not any of the Imams and scholars of the Muslims.” (Al-Fatawa Al-Kubra by Ibn Taymiyyah)
Ibn Al-Haj (may Allah have mercy on him) mentioned that one of the bidah on ‘Ashura’ was deliberately paying zakat on this day, late or early, or slaughtering a chicken just for this occasion, or in the case of women, using henna. (Al-Madkhal, part 1, Yawm Ashura)
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Courtesy: sunnahonline.com