There are some mistakes people make on the day of Ashura, such as wearing kohl, taking a bath (ghusl), wearing henna, shaking hands with one another, cooking grains or otherwise grieving!
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. “
“Because of the killing of al-Hussain(ra), shaytaan caused the people to introduce two innovations: the innovation of mourning and wailing on the day of ‘Ashoora’, by slapping the cheeks, weeping, and reciting eulogies. … and the innovation of rejoicing and celebrating. … So some introduced mourning and others introduced celebration, so they regarded the day of ‘Ashoora’ as a day for wearing kohl, doing ghusl, spending on the family and making special foods. … And every innovation is a going astray.”
To counteract the extreme position of the Shias, another extreme group called “the Nawasib(Nasibis)” took this day as a day of happiness. The Nawasib, which consisted mainly of the Khawārij, held animosity against Sayyidna Hussain(ra) and the Ahlal-Bayt. They celebrated this day by wearing new clothes, cooking special food and spending extra money on their family. These people now take the day of Ashura for a seasonal celebration like that of festivals and weddings.
Therefore, The Shiah and the Nawasib opposed each other by introducing an innovation in the religion. So while one group lamented and mourned on this day the other group celebrated and made it a day of happiness. As for the Ahl as-Sunnah they oppose both of these groups, neither making it a day of celebration nor a day of mourning. This is the established practice of the companions and the pious predecessors.
To conclude, what is authentically established from the Sunnah is the fasting on the day of Ashura. The Prophet (peace and blessings of Allah be upon him) used to be very keen to make sure he fasted on the day of ‘Ashoora’ because of its great status.
Ibn ‘Abbaas (may Allah be pleased with him) said: I never saw the Prophet (peace and blessings of Allaah be upon him) so keen to make sure he fasted any day and preferring it over another except this day, the day of ‘Ashoora’, and this month – meaning Ramadaan. “
“Today have I completed your Deen(religion)’ Whatever was not part of the Deen(religion) during the time of the Prophet cannot be considered as part of the Deen(religion) today.” Allah said.
Imam Malik also said: “Nothing will benefit the later ones from this Ummah, except that which benefited the earlier ones (i.e., the companions).”