Praise be to Allah.
Ahl as-Sunnah wa’l-Jamaa‘ah are closer to al-Husayn (may Allah be pleased with him) and the family of the Prophet (blessings and peace of Allah be upon him) than anyone else, for they are the ones who show love and respect for the Prophet (blessings and peace of Allah be upon him) by showing love and respect for his family, wives, companions and offspring, as Allah, may He be glorified and exalted, enjoined, without any exaggeration or negligence. The Raafidis do not have any advantage that gives them a special connection to al-Husayn (may Allah be pleased with him) or the Ahl al-Bayt (members of the Prophet’s family), such that they should be offered these condolences. In fact, in this regard their exaggeration, innovations and misguidance dictate that we should disavow them and denounce them.
For more details on the Raafidi sect, please see question no. 101272.
What the Raafidis do of venerating the day of ‘Ashoora’, holding gatherings of mourning, expressing grief and weeping in memory of the death of al-Husayn, with all the kinds of Jaahili wailing that they do, is a reprehensible innovation that was not done by the early generations, namely the Sahaabah, Taabi‘een and leading imams (may Allah have mercy on them).
It was not the practice of the Prophet (blessings and peace of Allah be upon him) to commemorate the anniversary of the slaying of any of the Prophets or martyrs, including Hamzah the leader of the martyrs (sayyid ash-shuhada’ – may Allah be pleased with him).
And it was not the practice of the early generations to c ommemorate the anniversary of the death of anyone, either the Prophet (blessings and peace of Allah be upon him) or anyone of lesser standing than him.
So whoever does that has fallen into innovation and is going against the Sunnah and the practice of the righteous early generations.
For more information, please see question no. 4033.
The Raafidis went even further in their misguidance and introduced on this day abhorrent innovations and grave evil practices for which there is no basis in the religion of Islam, such as striking the chest, rending the garments, wailing, slapping the cheeks, striking the shoulders with chains, cutting the head with swords and shedding blood.
For more information, please see question no. 101268
Based on the above, it is not permissible for a Muslim to offer condolences to the Raafidis for the slaying of al-Husayn (may Allah be pleased with him), because of what that involves of innovation and going against the Sunnah, and what it involves of supporting and approving of their falsehood. Similarly it is not permissible to say to them Ma’jooreen (may you be rewarded for your loss) because they will not be rewarded for their innovation; rather they are sinning and deserve to be punished.
And Allah knows best.