Praise be to Allaah.
It is not permissible for you to wear fancy clothes or
anything else on Aashooraa because that may make ignorant people or those
with ulterior motives think that the Sunnis are happy about the killing of
al-Husayn ibn Ali (may Allaah be pleased with them both), Allaah forbid
that that happened with the approval of the Sunnis.
With regard to your interactions with them by backbiting
about them and praying against them, and other kinds of actions which are
indicative of hatred, this serves no purpose. What we have to do is to
strive to call them (to Islam) and to influence them and reform them. If a
person is unable to do that, then he or she should turn away from them and
leave the dawah activities for those who are able to do them, and not do
anything that may put obstacles in the path of dawah.
Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him)
said:
Because of the killing of al-Husayn, the Shaytaan started to
spread two kinds of bidah (innovation) amongst the people: the bidah of
grieving and wailing on the Day of Aashooraa, striking the cheeks,
screaming, weeping and reciting eulogies ; and the bidah of expressing
happiness and joy. So some express grief and others express joy, so they
started to like the idea of wearing kohl, taking a bath, spending on their
families and preparing special kinds of food on the day of Aashooraa and
every bidah is a going astray; none of the four imams of the Muslims or
others approved of either of these things (either expressing grief or
expressing joy)
(Minhaaj al-Sunnah, 4/554-556).