What is the ruling on closing shops in mourning for martyrs, and on general mourning for them, and specifying special days for them, and eulogizing them, and adopting black banners, and making their graves prominent and writing on them, and writing poetry and chanting about them?

Closing shops and facilities and striking is permissible if its benefit outweighs its harm, and it is forbidden if the harm outweighs the benefit or is equal to it. The reference for this is the ruler (Wali al-Amr). Permissible mourning (al-Haddad al-Shar'i) is specific to the woman whose husband has died, so she mourns for four months and ten days as an obligation. As for the woman whose relative has died, she mourns for three days as a permissibility. It is not permissible to specify days for mourning that have not been authorized by the Lawgiver, and any innovation of this kind is considered a bid'ah (religious innovation). There is no harm in eulogizing martyrs if it does not involve falsehood or any prohibited matters. There is also no harm in displaying black banners. It is not part of the Prophet's guidance to make graves prominent or to write on them. His (peace be upon him) Sunnah was to level all elevated graves.